I'm a bit confused now, this is a gaming PC but you don't care about Crossfire? HD 4850 Crossfire is the best bang-for-the-buck gaming solution these days.
I'd suggest a P5Q Pro or GA-EP45-DS3R. They are only $20 or so more than similar motherboards with fewer features and with a single PCI-E x16 slot. They are not ideal for Crossfire, especially at higher resolutions, but they can do it.
Even if you're not interested in Crossfire, it's smart to pay the extra $20 and keep the option, It will increase the resale value of the PC, 2 or 3 years down the road when a HD 4850 is under $100. It also lets you add a $30 HD 3450 or something if you ever want to use 3 or 4 monitors. Maybe you don't care about that either now, but with LCD monitor prices plunging you may become interested later. I got burned that way last year - didn't expect I'd ever want 3 monitors, and now I want a third but can't hook it up.