If you're going to build an AMD system today, get an AM3+ mobo, which will leave open the possibility of upgrading to Bulldozer if that proves worthwhile.
The GTX560 may be overkill for your resolution, but will be future-resistant.
Rosewill is not one of my preferred choices for PSUs, although this one appears to be modern, and probably good for what's on its label (80plus tests at 100% load, although at an unrealistically cool 23C). Seasonic, Antec, Corsair, XFX, and Enermax/LEPA are among the better brands.
For $110, the X4 955BE is the better processor choice. With its unlocked multiplier, you can get a $30 Xigmatek Gaia HSF and probably overclock it to at least 3.6-3.8GHz (some people have broken 4GHz).
Still, with a $600 budget, you're in range of a better-performing Sandy Bridge build. Start with the recent $526 SBM machine but get a better motherboard, and maybe a better PSU, and you'll outperform the AMD machine except in heavily threaded applications.
Read the discussion that follows it though. The additional money in your budget can easily overcome what I (and others) thought was a poor choice of mobo. You can also get a better PSU, like an Antec HCG or Corsair Builder.
The 945 is 95 watts and the 3.2ghz BE is 125 watts. The 945 can still overclock with the fsb. The 955 is easier to overclock since the multi is unlocked, but its binned to be a 125watt chip and needs a aftermarket heatsink to do any real overclocking. The 945 used to be more expensive than the 955 because the the phenomII's that bin to a lower wattage are rarer.
The 945 vs the 955 question is not that easy to answer.
The 945 is actually binned better closer to the 975 but the multi is locked.
Overclocked both should top out at about 3.4ghz with the stock coolers, the 945 might be better with the stock cooler than the 955.
-The 95 watt 945 is better to get if you are getting a am3+ board because when you go to sell it used, most boards that have the athlonII x2,x3,x4 on them like package systems have am2+ or am3 95 watt boards and can't use the 125watt cpus. So later on the 95 watt quad should be easier to sell used.
Most of the people with budget boards with semprons, regor's or x3's on them have the cheaper 95 watt boards.
-Its cheaper to get the better binned 965 3.4ghz than buying a aftermarker cooler and the 955 3.2ghz.
The 965 will do 3.6ghz on the stock cooler.
asus am3+ board that supports ddr3-1333 (dont get the gigabyte it is a ddr3-1066 board) http://www.newegg.com/Product/Product.aspx?Item=N82E168...
$64.99 ASUS M5A78L-M LX AM3+ AMD 760G Micro ATX
It looks like this board lets the memory overclock to 1600ghz with the fsb increase, a bit of extra memory voltage, increase the cpu voltage a bit, then increase the fsb. Seems like this board would work out with the 945.