GFX: Don't go over the top with new/fancy. Go for something with good support. That means Radeon graphics, not older than 7000, not newer than 9000 (which means stay away from the R300 chip until the support in Linux get's to a certain point. I don't remember if anything has been said about OS4 support for these cards, but I think it's fairly safe to say that OS4 might not fully support R300 either ;-) ).
Sound: It's onboard. If you want S/PDIF (I never can remember where to put the slash, but at least I try :-) ) go for SB Live! or something, but don't get an SB128 to replace the onboard sound until you know you need it. For Linux you won't need it, for AmigaOS you might, but I bet you'll save money by not buying it before you need it.
Ram: Please don't try to cheap out here. If you want memory that doesn't work it's EXTREMELY simple to shop ;-). However, if you want everything to work from the start, either order memory from the A1 dealer, OR buy a module that has full support in all columns here:
AHS, memory subsectionNIC: onboard, should work for most things.
Disk: All modern drives should work just fine.
CD/DVD: I've had problems with a PlexCombo, everything else seems to work. I say seems, but take a look at AHS from the above link anyway.
That's basically that. Good luck with your decision.
