Best place to learn all the hardware options for an A1200/A500+

[Argus]

For maximum games fun, I recommend a Phase 5 BlizzardIV 68030 board @50MHz with the optional SCSI 2 board.  Plop a nice big & fast 2.5" ide drive on the internal harddisk interface and use the scsi on the expansion board to run an external scsi tower with your cdrom, extra harddrives, scanner, etc.  You can mount a 64MB simm on the accelerator and a 128MB HP simm on the SCSI expansion board to give you more fast ram than you'll ever use.  Power the whole lot off of a PC AT or ATX power supply in the adjacent tower (you'll need to make or buy a power adaptor from Amigakit or elsewhere).  Put a Silversurfer or Twister fast serial card on the internal clockport and you can have a fast dialup internet connection for on-line gaming and downloads (but don't expect to play deathmatch Quake games).  Or if you have broadband, put a 3Com or other compatible type (wireless even) nic card in the pcmcia slot.

[Argus]

Price depends on whether you stumble upon a used system cheaply or buy on eBay or elsewhere where retro computer prices have skyrocketed.  On eBay, you could probably expect to pay $200+ for the system I described or individually much more to construct (i.e. $100 for bare A1200, $150+ for BlizzardIV, $80 for SCSI board, $20 for 2.5" ide drive, $15 for 12x scsi cdrom, $30 for Silversurfer/Twister board, $10 for 3Com pcmcia...not including s/h).

I've heard people have good luck putting ads in local papers offering to 'dispose/take care of' old Amiga stuff.  Probably worth a 20 cent personal ad.