OP, you aren't even close with those statements.
7800GTX512 > 6800GS-SLI >= 7800GTX > 7800GT
7800GT-SLI > 7800GTX
7800GTX-SLI > 7800GTX512
7800GTX512-SLI > ALL
Lots of reviews and benches out there, just search.
P4 @ 3.8
6800GTo 256mb DDR3 PCI-E
6800GTo is from a dell, it's a failed ultra. (dual slot) Has 400/1000 clocks, I don't overclock it, but it's only 12 pipe with 6 shaders. I get ~5400 in 3dmark05. 2gigs is for BF2, I get very good framerates @ 1280x1024, mostly at...
Hot CPU Tester Pro 4.2.2(Lite Edition)
Called Hot CPU Tester, load it up and run the diagnosic check, post back which one fails. It'll test more then the CPU, including ram since you don't have a floppy for memtest.
I just got a Asus P5DL2 945P motherboard and transplanted my dell 8400 guts. It's running a 540, but the vcore on the monitor going anywhere from 1.42-1.48 constantly, it just bounces all around. In the bios it's set to 1.40
It's also showing:
3v - 3.31
5v - 5.04
12v - 12.20
All it does is allow the CPU to default back to 14x by "tricking" it back to defualt of 14. If you have a 3.2 then your option will be 16 or 14, 2.8 will only see 14 or 14. Asus has had this for awhile before Abit published this.
It seems the last batch of 6800GTOs that came from dell you can't unlock the last quad. Not because it's bad or artifacts, just because rivatuner can't do it. I have a thread going over on guru3d to the maker of RT. Anyway your 6800 3dmark seems low, on my 3.2p4 I'm getting almost 10900 stock...