Hello Sean, and welcome to SPCR:
I doubt that you'll get flamed; we're pretty civil 'round here in general...
Looks like you have a good start on a system. I have a couple of questions/things to check (that you may have already considered):
Is the MSI compatible with a mobile chip? If not you should consider a Athlon 64 2800+ and/or an undervoltable motherboard like the AOpen.
The trick with a Zalman 7000 and the Evercase is to make sure the socket is located far enough down from the top of the motherboard so that it fits. The Evercase, while excellent for air flow, is vertically compact. There is only about 3/8-1/2" from the top edge of the mobo and the bottom of the PS. And some motherboards (like the Neo Platinum) seem to possibly
have the CPU socket fairly low
and thus might cause the 7000 to conflict with the video card -- though this is just cautionary speculation
on my part...
Heat speaders on RAM are probably not helpful or necessary, and it might even prevent better cooling. I would check MSI's RAM compatibility list. I have only used Mushkin in the four Athlon 64 machines that I have built, and in one case it was their "economy" sticks of 512MB -- they worked fine, and they are an incredible value:
The great thing about the nForce3 250 chipset is that it seems to be able to run 3 (and even 4) sticks of RAM at DDR400. It's too bad the AOpen board still used the 150 version...
As for the Linux video card, this is always a challenge, isn't it? I have Suse 8.2 Pro running on three machines, and frankly, IIRC ATi had better driver support. One of the other machines has a Matrox P650, and it works, but "barely" with no 3D. The third one has onboard nForce video and I have had real issues getting 3D to work. Also, you'll want to confirm support for the onboard LAN -- I had to add Realtek cards on the two Athlon/nForce machines.
You'll also want two good quiet 120mm fans, (though maybe one if you have AC?): the Nexus works quietly even at 12v, or the Enermax is quiet (and moves more air) at 5v or below than the Nexus at 12v.
A little tip on keeping two HD's cooler in the Evercase: mount the drive that is below the other upsidedown
so that the circuit boards on the two drives "face" each other. This will let a lot more air flow pass between the drives...