Well, the next largest area for conflict is either Sound card (win 2k at least) or a network card. The network card is more involved simply because of additional protocols and setup but it also is really deeply linked to the OS. Go for a quality 3com, intel or "something else" NIC. I am running a 3com 905C 10/100 and haven't had any problems. I think the moderator of this forum (palandri?) suggested Intel because they actually make all their own components instead of buying chips from other people and assembling a NIC from them.
While I haven't had problems with 3com others have. You never know until you plug it in. These two are ones that you will normally install next, but if you run a RAID 0 setup or something DEFINITELY do that first. TONS of posts here on RAID. My recommended order: RAID, NIC, SOUND.
LUCK!!!!