They are 940, not 939. There is no opteron on 939. It's the same socket, with 1 more pin though... If we just knew which one, maybe cutting it would do the trick
I'm probably sure he won't be able to find anything else then a barton 2800+ OR a barton 3200+. There's nothing available anywhere in our providers stock for 3400+ or even mobile ones (except thurions, not sure about how you type that). Semprons on socket A just stopped being available like a month ago, now we can only get socket 754 Semprons "64", which is the same crap. Actually they're not THAT bad, it's not like you had a Celeron or an old Duron, but they're not the best performer either.
Opterons are fairly expensive, and personnally if you don't want to change your video card i'd go with an Asus A8V (not that I like Asus much, but you won't find any board with AGP8X that has a socket 939 and decent specs elsewhere) and an AMD Athlon 64 3200+. Something like 250$ US worth i'd say.
Edit: DUH, just re-read your post, you want a new vid card! Ok, it's going to be pricey but it's worth it.
Asus A8N-E (nforce 4 chipset, awesome as always) ~ 110$ US
Nvidia 6600GT 128mb DDR3 on PCI-express from eVGA, Leadtek, Gigabyte or Jaton (just the cards I had good experience with, recommendations ya know) ~ 150$ US
AMD Athlon 64 3200+ ~ 155$ US
Total: ~ 415$ US