I have many amps, both ones I've made myself, and "brand" names.

Marshall, Fender, Peavey, Vox.... from my 5w "Champ" home brew, upto a 100w Marshall.

Is there one amp that does everything? Kind of!

Sometimes it just whether it is easy to lug a big rig (eg. quad box) to a gig that only needs low power ...

When you choose your amp(s) these are a few of the checklist items I advise.

POWER
It isn't just the output of an amp (and always go by the "RMS" power, not peak).

SPEAKER(S)
A very efficient speaker sounds louder than an inefficient one.
A 15w amp with an efficient speaker will probably sound as loud as a 30W with inefficient speaker(s).

Multiple speakers tend to sound louder, and open back cabs "throw" more sound around.

I build boxes and heads separately so I can mix and match.

I have made quad boxes with 4 x 8" and 4 x 10" ...both sound great, and the 4 x 10"
throws a lot of sound.

I have closed cabs with 2 x 12" and 4 x 12 " as well as open 2 x 12".

Of course, you should always try to match the output of the amp with the power handling, and impedance,  of the speaker(s)...but you can get it wrong both ways.

A small amp clipping at full tilt can burn out a speaker that is rated well over the power (ie a 20w amp can "blow" a 30w speaker...the clipped waveform often overheats the voice coil.)

And, of course, a 50w amp going hard will probably blow a 20w speaker.

BUT for lower levels, and in the "clean" zone, harm tends to be minimal.
A clean sound at lowish power from a 50w amp won't usually harm a 20w speaker.

Also, the impedance of a speaker/amp are not actually constants, this varies with the frequency, so sometimes a certain amount of mis-match isn't that critical, but of course, the lower you go (ohms), the closer you are to a short circuit! (not good... be careful with multiple or extension speakers.)


TUBE or SOLID STATE?
Both can be good or bad.

I run a little Peavey Backstage that sounds pretty good for average and lower level gigs.
I actually use it to record (but I run the guitar through a tube preamp first to do this.)

It has respectable built-in reverb, and some good overdrive sounds, and does a fair job "clean." For bigger gigs, I would go for a 100w running lower output.

Providing the amp is reliable and sounds good to you, then go for it.

Personally, I still prefer a good tube amp (my home made Bassman thru 4 x 10" sounds really good) and experimenting with tubes is worthwhile.


TUBES
Sometimes you should ignore the "common" wisdom.
For example, although there are good sounding 12AX7s out there, I generally prefer a lower output level tube like a 12AZ7... gets me better cleaner tones.

For output tubes, and clean sounds, nothing sounds better to me than a KT66 (including the better re-issues.)

Solid state rectifiers are fine if you don't need "sag" or "compression" in the amp (try a pedal.)

For distortion I have a different view.
I generally go for an amp that sounds good "clean" then use a pedal or other distortion devices rather than running the amp hard (although with smaller amps this can sound great, too!)

It is harder to get a good clean sounding amp than ones that distort ...and don't clean up at lower levels. I also prefer having a good sounding reverb in the amp.

I have a truly awesome sounding 30w tube amp from the early 60's, but it has no really "clean" settings...so that limits its use at gigs.


MATCHING
The next thing that is really critical is the combination (especially "front end") match of the guitar, the amp, and the speaker(s).

I have some amps that just don't like humbuckers ... and often you might think that an amp "sounds bad" when in fact, it just doesn't marry up with the guitar you have plugged into it.

Really bright speakers may be too harsh with single coil pickups, and prefer humbuckers. Or they might just give you the "Tele Twang" you love.

So, even with some of my "legendary" amps, I have to be careful with the choice of guitar I use, some sound a lot different with alternate guitars.

The marriage of Fender guitars and Fender tube amps is pretty much a religion, and rightly so (ie single coil pick-up types).

However, as soon as you put a stomp box in the chain you have another big variable.

The best thing you can do is use your ears to see how your particular sound is best
achieved. Higher output pickups will drive most amps harder..so more distortion, even at lower levels.

STAGE
Also, I can create almost ANY sound in my living room, but once you get on stage, with other players, and room acoustics, all that goes out the window.

A closed speaker box tends to project the sound in a narrower path than an open back, and tends to have more bottom end. That may mean that a few rows back, the guitar is loud but dull. Equally I have played my little Deluxe Reverb (about 20w) and the sound was razor sharp (too much so?) at the back of the room.

So, when you get to a gig, try to have your speakers throwing some sound at your own ears if you want to hear what is coming through..and if possible, get a check from further back in the room.

FINALLY
So, some answers! will one amp do everything? I don't think so, but start with one that sounds good clean, and upto levels you will use (whether at a gig or at home).

Find a good pedal or two for overdrive.

Find reliable ones, and be careful with the impedance, power handling, and actual "tone" of the speakers. Some "great" speakers don't always marry to certain amps.

Some really cheap, unknown ones sound great.
Some of my best were found on junkpiles.

Consider having separate boxes and heads, both for easy of lugging and for getting different sounds (but watch power handing and impedance.)

Listen for the best sounding combinations of guitar/amp/speaker.

Having tried lots of "rigs" I tend to go for simple set-ups, and ones where if one thing "goes down" you can still get a good result....the more pedals, the more chance of something not working.

Lastly, remember a great performance with lots of enthusiasm counts more to an audience than "perfect" sounding gear, and once in a mix, it sounds very different to the way you practice at home.

Use your ears, and always get gear that makes you want to play.

Personally, I would say, if you just play at home in your bedroom, go for a 10w- 20w amp with a few great sounds. Anything down to an 8" speaker will probably be OK.

For most gigs, anything upto a 45w - 60w amp (preferably tube with reverb) will
cover a lot of ground, especially with 2  x 12" or 4 x 10".

Beyond that, bleeding eardrum music might mean going for a legendary stack.

But at my age, as well as my ears, I have to watch my back.

If we could all afford roadies!