ASUS P5E vs P5Q vs P5N-T Deluxe

I have a P5N-T running the second newest BIOS 1301 I think - think 1401 is the latest.
Anyway, I have pretty much the same as what you're looking to build - Q9550 and 4gb Dominators (4x1gb). I've found the board is stable and runs well on the 1301. No issues with Vista 64.
Did have an issue on older BIOS with XP and SATA optical drives which would cause GTLDR errors - fixed this with the 790i SATA driver, but as I say no issues with latest drivers/BIOS/Vista64.
However, I would only get the P5N-T if you will definitely use SLI in the future, and moderate-high overclocking won't be an issue in the future. The 780i is not good at clocking quads - I can only reliably get 400 FSB (3.4Ghz) with reasonable northbridge volts, whereas I could get 475+ with a dual. The Intels are stonger chipsets IMO, so only go with the P5N-T if you will use its unique features - I.e Sli.

Well, P5N-T will beat the other MoBos regards to its high end features but user reviews on newegg are saying that it isnt a stable product.

Other models are stable and bug free, but there is no SLI support. They only support the CrossFire  

Any ideas about a good SLI enabled ASUS MoBo that I can attach a Q9550 and a PCI express 2.0 GPU + support of high speed DDR2 memory [non-OC>800]

This is a good I've had no problems with it http://www.newegg.com/Product/Product.aspx?Item=N82E168... or this is even better http://www.newegg.com/Product/Product.aspx?Item=N82E168...