Give me help with selecting a mainboard, plz?

Hi all, I could use some help selecting a motherboard. I haven't been up to date with hardware, so I'm not sure what some of these new boards are all about. Here's what I'm looking for:

-Prefer AMD boards, since thats what I'm used to. If anyone can give me a good reason to switch now, I'm open to change.
-I would prefer to use an nvidia graphics card over an ATI card, but I don't plan to put more than one in SLI
-I'm looking in the <$175 price range
-I plan on using this for gaming, so onboard graphics is not so helpful
-I liked the 590 boards (some more EVGA stock just popped up!), but I'm not sure if these boards are still in favor.

Other than that, I'm open to suggestions. Also, could someone explain the new levels of mainboards? I only remember back to the 590 boards, so whats these 750a and 780a boards all about and how they compare. I'd also appreciate a suggestion for a matching cpu, something in the <$150 (I used to like the 2.5 GHz Brisbanes).

Thanks much for any advice! -RP