In case this might be of some help some out there who have somewhat large systems, I thought I'd post my ongoing experience getting a new i7 DAW with a P6T Dlx V2 mobo configured. My hardware setup consists of:
RME PCI interface, MADI and AES32 in a Magma 13 slot chassis interfacing with either a PCI or PCIe host card.

Multiface
MYtek Stereo AD/DA
ADI-2
4 x ADI-DS
2 x ADI8-DD
UAD-2 Quad
Duende

This has been running very smoothly for over a year using a Gigabyte GA-EP35-DS3 mobo and  Intel Q9450 OC'ed to 3.2GHz, but I've been getting unacceptable VST spikes in C4/C5 when running large tracking sessions at 128k buffers. I decided to try to up the ante with a much more powerful i7 processor.

A PNY Quadro 4 x head graphics card is essential to my setup so everything is predicated with compatibility with this. My existing hardware configuration is working like a dream as far as my routings are concerned. Having x44 AD's and x44 DA's along with 10 pairs of AES/SPDIF allows me to hard wire in all of my hardware to the RME I/O. I use Cubase just like a big digital mixer spread out over 4 x 24" Dell 2407's. I'm not sure if things would change with a different video card, but it really doesn't matter because the Quadro is going to have to be the graphics card......soooo........with the Quadro in PCIX16_1......:

Sunday:

Scenario 1. , PCIEX4_1 on the P6T Dlx V2 mobois too short to work with any PCIe card except my Magma PCIe host card for the chassis hosting the Multiface, MADI and AES32 cards. It worked in this slot until I installed the UAD-2 or the Duende in PCIEX16_2. Then the computer wouldn't boot, requiring a shut down, removal of the battery and resetting of the CMOS.

Scenario 2. If I switched back to a Magma PCI host card for the Magma hosting the RME cards and inserted it in PCI slot #1 with either the UAD-2 or the Duende PCIe card in PCIEX16_2, I got a nothing and I had to shut down, remove the battery and reset the CMOS.

Scenario 3. If I inserted the PCI host card for the Magma hosting the RME cards in PCI slot #2 with the UAD-2 or the Duende PCIe card in PCIEX16_2, with either the UAD-2 or the Duende the system booted and ran smoothly so at this point I could use my RME cards and either my UAD-2 or my Duende PCIe card.

Scenario 4.If I inserted the PCI host card for the Magma hosting the RME cards in PCI slot #2 with the UAD-2 PCIe card in PCIEX16_2 and inserted the Duende PCIe card in PCIEX16_3, the system wouldn't boot and requireed a shut down, removal of the battery and resetting of the CMOS. Same thing happened if I switch the Duende and UAD-2 in the different slots.

Also, during the day I had done a lot of experimentation with loading the DSP card and/or my Magma host cards (both PCIe and PCI) in different orders. Sometimes, when the DSP card was installed and a good boot was achieved and I then loaded the Magma host/RME card, the computer would boot up, but the drivers for the RME cards wouldn't load. There was obviously some kind of trainwreck happening.

After trying the aforementioned unsuccessful Scenario 4, if I went back and tried to use the previously successful Scenario 3 , I couldn't get Scenario 3 to work at all.

Yesterday I was able to get the system to work with the Magma PCIe Card in the PCIEX4_1 with the UAD-2 in PCIEX16_2 and the Duende in PCIEX16_3 by adjusting the settings under Advanced/Chip set/North Bridge Chip set Configuration to the 16x 1x mode. This worked perfectly and I ran a test with x 24 live inputs recording at 32k buffers (0.7 ms latency-I have the most recent HDSP drivers (and current drivers for all other hardware in the DAW loaded). It was unbelievably smooth and the VST meter in Cubase 5 was only showing 3 little bars.........no spikes or dropouts......rock solid.......then I went back into the BIOs and made a few adjustments to get the memory speed optimized and the whole thing fell to pieces. I reset the CMOs back to square one (where it was working before I tweaked it) but now Windows won't load at all. The machine posts, but I just get the eternal scroll bar as XP tries to load.

My current Intel Quad DAW uses a Gigabyte GA-EP35-DS3P mobo. This mobo is totally compatible with all my hardware. I have seen some online threads mentioning good success with a Gigabyte GA-EX58-UD5 mobo. Not the same hardware config I've got, but it's certainly worth a try at this point.

This configuration has been a challenge. The Gigabyte GA-EP35-DS3P on my Intel Q9450 based DAW inspires quite a bit of confidence. It's very friendly with the RME/UAD-2/Duende hardware. I've got a Gigabyte GA-EX58-UD5 mobo on the way here. Life's too short to keep tweaking this ASUS mobo. I'll say this for the ASUS though, if someone was using a simpler (and compatible) hardware setup, they'd likely be happy with the performance. The DAW ran like a bat out of hell there for a little while.

Any suggestions or insights relative to this would be welcome.
HeadScratch