For a single worstation + F@H cruncher setup and with your new ±1000U$ budget, I came up with the idea listed below. All prices are from NewEgg.com again, although I'm sure you could get several parts for les at some local stores.
2x Athlon MP 2000+ retail - 157$ each
TYAN Tiger MPX S2466N-4M - 195$ (but currently B/O at NewEgg, not hard to find elsewhere)
512MB DDR PC2100 ECC Reg. - approx. 180$ (there none at NewEgg, what a shame)
Your Radeon 64MB DDR
The 3Ware Escallade 7000-2 from HyperMicro - 135$
2x WD800
JB in special this week-end at 106$
Lite-On LTD-163 DVD-ROM (why a DVD on a workstation...nevermind)
Floppy 9$
Either your Antec enclosure or the new SX835II with a 350W PSU - 86$
1168$ if you buy the SX835II
Ok, I busted the 1000$. Still, this is way better both in term of reliability (read my thread about the server with the TYAN motherboard?) and performance. The PSU inside the SX835II has dual fans and meets AMD's requirement for a dual-Athlon MP setup. It's not metallic grey, but you asked for a
usable workstation, so I figure that you can use a box even if it's not all shiny. As for the Special Edition Caviar, they are only 11$ more each than the Samsung P80 (with a 2MB buffer). And the SE Caviar will keep their 3 years warranty after October 1st, so the risk is small. I found 512MB ECC Reg. stick for only 156$ at
NCIX if you want to save some $$. Although it's marked as generic, it should be quite stable nonetheless.
You could also opt for Athlon XP 2000+ at 109$ and do the pencil trick. That would bring the cost down to 1072$ for the whole system.
I wrote that the Mushkin memory is expensive because here I can get perfectly respectable unbuffered Samsung 512MB PC 2700 sticks for much less. I would say
around 135U$. Besides, if you search a bit more on NewEgg's web site there are nice Kingston 512MB PC2700 RAM for 149$.
Two other deals I saw over at NewEgg : Athlon XP OEM for 55$ and ECS K7S5A also at 55$ (despite all Tony has against it, it still has a rating of 4/5 stars from some 500 users - not all that bad).
Regarding the GigaByte motherboard. A store I often go at and perhaps the only one where I trust the competence of the sellers (because they are in fact technicians, with a clue in bonus) sold the KT266A an KT333 versions of the GigaByte as their default brand. The BIOS support of the both versions was very good and the stability was without reproach too. According to the few comparative reviews I read, it wasn't the most optimized though (although it wasn't as pathetic as the MSI), but in the middle of the pack. Since you (wisely) place reliability over pure speed, the GigaByte is one of your best bet IMO. I wouldn't see why their new KT400 would be worst than the two precedent versions since the KT400 is mostly a KT333++.
And nope, I don't trust Promise controllers very much, just a little more than the HighPoint. That's why I didn't offered you the version with the onboard controller since I believe it would be a huge step back from the Escallade you are planning to get instead.