I want to build an AMD machine for around $600-700. I will use this machine for Gaming mainly for the new games coming out over the next year. SW: ToR, Diablo etc.
I have not built a machine in 10 years so I am a little out of pratice but in the past I have been partial to MSI, Asus and have used Gigabyte but I am not tied to those products. For Video Cards I am partial to NVidia but am not tied to those either if an ATI has better performance at a better value I am all about the best machine for the buck. I will not add another video card later on either so a machine that supports only 1 video card is fine(unless you guys give me a reason why i should in a year or so add another videocard) but I will be using two monitors. I use two monitors when I work from home.
There is really no replacement available atm for the Asrock 970 Extreme 4, especially if you want to have a choice to crossfire.
If you don't need crossfire, then there are ok AM3+ boards around the $100 mark that would work.
Get a Radeon 6870 they are really agressively priced atm.
There is a sale going with the GSkill 2x4GB 1.5V CAS8 1600Mhz ram $59.99 - that would be great for you.
Going for the Phenom II x4 955BE for CPU would be adviceable.
Then if you do want to Crossfire, a slightly bigger PSU would be in order, the Antec HCG-750 does have a nice rebate atm.
That's a great PSU, however, I'm no expert in SLI or crossfire check with some of these other guys to see if 750 watt is enough for your particular intentions although generally speaking I think 750 watts is a decent amount for it.
Either go for a AMD Phenom II X4 955BE or a Core i3 2100.
The AMD quad core is better in multitasking while the Core i3 is better for gaming.
They both would just cost a few bucks more than the X4 945.