It's incredible to see how cheap some of the off-brand equipment is on eBay. Names like Pyle, Legacy, Pyramid, Dual, etc. that offer 800 watt speakers for $10 a pop.

Are they any good?

To be fair, My experience is entirely with Legacy and Pyramid; I have not tried Pyle or Dual branded equipment. However, they all often have similar specifications and price points.

I bought some "800 watt" Legacy 3-way speakers a while back on eBay for $25 + shipping - I think it ended up being about $35 to my door. Seemed like a great price for a great pair of speakers...after all, my stock speakers were only rated at 10 watts! However, upon closer inspection, I found that "800 watts" is often measured as either "Music power" or "peak power". "Music power" is not a useful measurement. "Peak Power" is misleading. 800 watt peak power often means "pair, peak to peak", meaning that its adding the two speakers together. Lets do some math:

800 watt peak-to-peak, pair = 400 watt peak to peak per speaker
400 watt peak-to-peak = 200 watt peak
200 watt peak = 141.4 watts RMS

RMS is a useful measurement but even then, I am highly doubtful that any Legacy and Pyramid branded product would operate at 141.4 watts RMS. Mine didn't even come close. To put things into perspective, most good headunits put out 50 watts per channel. Thats at full volume.

 Looking at the specs again, I noticed that the "Frequency response" was 80 Hz - 18 KHz. Although wattage is important, wattages are often distorted or misrepresented because it is often misunderstood as the only performance metric. Perhaps more important is freqency response, as this determines how deep the low sounds are and how crisp the highs are. 80 Hz is NOT a good low range; If you look at high quality speakers, such as Alpines, they often go as low as 25 Hz. Decent name brand speakers usually at least go down to 40 Hz. an 80 Hz low range will result in muddy, "buzzy" sounding bass, at best.

Same goes for the high range. 18 KHz is not good at all - 22 KHz should probably be a minimum acceptable value, with many good speakers breaking 30 KHz.

On a personal note, the Legacy speakers I installed sounded marginally better than the stock ones, but not by much. They did not take much bass before they started distorting the sound and they were too tall to fit in my speaker enclosures. I had to modify them for them to fit.

I've also had some experience with a Pyramid cd player. Flashy colors and graphics but not a very good unit, in sound quality or features. It didn't even have a equalizer.

My advice would be to stick with the name brands. Alpine is top notch but expensive. Brands like Pioneer, Kenwood, and Sony are all good and less expensive and should be a considerable improvement over stock systems.