With Leopard release coming out in October it might be good to know before you purchase that new/used/refurbished macintosh on ebay wether or not you'll get all that is Leopard OS X 10.5. Apple has not released requirements as of yet, however we have gathered and found some prerequisites for the developer version and feel these will carry over to the production version.

PowerPC Based Macintosh Systems:

• PPC G4 or G5
• 256mb of Ram is somewhat stated however we feel 1gb should be considered the Minimum.
• 8gb of hard drive space - Please keep in minc that OS X requires 20% or 10gb of free space at ALL TIMES. So a 40gb drive should be consumed with 8gb of OS, leaving 4gb free at all time gives you 28gb of usable space.
• ATI 9600+ or Nvidia GeForce 6 series or better will be required to USE Core Animation. This feature will self shutoff and not be used when it the video card can't run it. So even if you have an older AGP video card Leopard will run however the some of the fancy graphics will not be displayed.
• Graphics card with at least 32mb of Ram should be considered a requirement as 16mb video cards fail to deliver that "AWE" Apple expereince. 16mb cards can be upgraded in AGP Based Mac's. G4 based laptops all had 32mb video cards.
• Those running the first Gen G4 AGP Powermacs should begin shopping for an AGP card from a Quicksilver model as they will get teh ATI/Nvidia cards with 32mb+ and should be compatible in the 4x AGP format.
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Intel Based Macintosh Systems

• Any Intel CPU
• 512mb of ram is being called by Apple but we feel 2gb should be put into every machine. The Mini's, iMac's and Books all run 667 200 pin PC2-5300 ram and 2gb (that's 2 1gb sticks) will run you about $80 new. Installation on the laptops is fairly easy, Mini's and iMac will require some extra effort. To find a local Apple support/service center you can call Apple directly. Also most Apple stores charge a modest fee for this service and it doesn't VOID your warranty. Installing Ram yourself however does according to their terms of service, so keep your old ram and stick that back in should you need warranty repair.
• MacBook's, Base iMacs and Mac Mini's all used the Intel GMA 950 graphics chipset. While this chipset is pretty good it is not 100% Core Animation compatible. Sorry. There is no upgrade option. Most visual effects will display but some will not. This won't hamper your experience at all, in fact it took a few days before we noticed it.
• MacBook Pro's, Mac Pro's, iMac's with onboard graphics chips by ATI/nVidia will be fine. There's no need to upgrade or do anything.

One last note:
     An external hard drive in a FIREWIRE case should be purchased or assembled. You can find Firewire external cases on Ebay and find a compatible hard drive, put the two together (this is by far the easiest thing you'll ever do with hardware) and you'll have your external hard drive to use Leopards built in Backup system. Trust us when we say, YOU'LL WANT TO DO THIS! The cost is less than $100 for most people. We are recommending a drive with 2-3x's the size of your current drive. Sounds extreme I know but this is going to serve your needs for years to come and you may at some point upgrade your existing drive. 

Well I hope that helps you with your upcoming purchase. Thank you and don't forget to check out our store.