Ok, a good few months have passed now, for those who remember this thread I'm happy to report that my rig is finally up!! (This is an initial report after having done one race, I may report back with more if there's any interest once I've gotten some more time with it.)
First of all, I got a P35 Blitz Formula motherboard in August, along with a 8800gts and a 7300 silent pcie card. CPU a Q6600, 1066mhz Memory; clocked to 3ghz initially.
With this config I hit a major bump in that the PCIEX drops to 8x even though I'm not running SLI/Crossfire. I was expecting it to stay at 16x 4x but it goes to 8x just having two cards inserted; this is pre-bios stuff so cannot be changed.
Whilst working fine in windows for 3 screens, 8x caused severe slowdown / sound stuttering in games like STALKER. In LFS 1280x1024 + 1920 +1200 + 1280x1024 got me around 40fps, however I didn't test it too much.
So I changed my strategy; I shelved the 7300 card and decided to wait for the X38 and then put the P35 board into my quad core Zalman HD HTPC project -- and get the X38 Maximus Formula for my main.
This has just been completed, with my pre order I was amongst the first in Australia to receive the Maximus SE from Scorpion Technologies.
The X38 features PCIE2.0 with dual 16x bus speed. To get straight into the meat, I'm getting 60fps and up (seeing 90 at times) in LFS with AA at default (i.e. off) but all details at max . Haven't finished tweaking it, i.e. no OC of the 8800gts yet but it performed flawlessly in last Monday's league race with around 20 cars on the track starting from the back (might have been slightly less than 60 then but no slowdowns experienced; wasn't looking at the FPS) of the grid (didn't get to do any praccy due to the reformatting etc required, finished setting it up all the wheels, teamspeak trackir only 15 mins before qual...).
(I may try turning side screen resolution down further and enabling AA, however didn't see any jaggies due to the increased distance to the screen so might just leave everything as it is now. Even though side screens are 1600x1200 screens, using 1280x1024 has no perceptible difference as the side screens are "distorted angle" / peripheral vision only.)
So my word of advice is, if you're buying a system now with the purpose of SoftTH, AVOID the P35 and GET the X38.
Dual 16x bus is quite obviously a massive boost for SoftTH which makes sense as the 2nd card gets its data across the bus 4 times faster than where your second card is @ 4x multiplier. Not sure how much the quad adds to it but look at this way, I'm running teamspeak, g25 wheel and trackir drivers - these are all separate processes, so quad can't hurt.
A triple rad Laing D5 Watercooling kit is coming my way soon and aim to get the speed up a fair bit from the 3.08 I'm running now. Will report back on LFS performance then.
Final word, as a first impression I'm stoked with having a 24" in the middle at native res and getting the side screens working perfectly with SoftTH. It's not been cheap, but I'm going to spend many, many hours over the next few years enjoying it.
Great work Kegety!