Disclaimer: the following was written while drunk after a long (8am - 8pm) day at work

Brands are a bit of a personal choice thing. I like MSI, Gigabyte, Abit and EVGA but that's just me; can be a tough choice.

But the other specs are a bit easier. Choose Core2, Nehalam or AM3+. I'd be looking at Nehalam or Core2 personally. Core2 for cheaper but still very good performance, Nehalam if money's no object. If you want AM3+ I think you need to wait a month for the new ones, but I don't really keep up with AMD these days sorry.

For Nehalem X58 is the chipset (does SLI and Xfire). For Core2 there's basically Intel (X38/48, does Xfire) or NVidia 750i/780i/790i does SLI.

To choose between X38,X48,750i,780i,790i choose DDR2 or DDR3 RAM.
DDR2 = X38,750i,780i
DDR3 = X48,790i or X58 if you're looking for top notch.

Then choose Nvidia (SLI) or ATI (Xfire).

I went for the 780i FTW (EVGA) which is Core2Duo (I have a quad) and SLI capable. It's a nice board, but not as solid as the Intel; main reason I chose it was SLI.

Sorry if I'm rambling, but basically the CPU, GPU and RAM you want will determine the mobo you need. From there it's brand, reliability/overclocking and peripherals.

Now I'm off to iron a shirt for work and go to sleep. Good luck with it