For gaming purposes, I would say that build is actually worse.. I didn't think about how cheap a GTX 280 would be nowadays, I didn't think they would even still have them on newegg... That card was the very top-of-the line in it's day, and will still be a bit better than brand new low end cards like the GT 640. Your first build would actually be better, since games depend more on the graphics card than the CPU, and the fx-4100 is still a good CPU.. However, there is still room for improvement!! You could get a cheaper motherboard and then put the money saved towards the video card.. Since your budget for the motherboard and video card is~$240, a better choice would be
Motherboard:ASRock 970 EXTREME3 AM3+ AMD 970 SATA 6Gb/s USB 3.0 ATX AMD Motherboard
Video Card:EVGA 01G-P4-3650-KR GeForce GTX 650 Ti 1GB 128-bit GDDR5 PCI Express 3.0 x16 HDCP Ready Video Card
Really there is no point in paying extra for a motherboard that supports SLI/Crossfire... Your 600W power supply couldn't even handle 2 GTX 280s. You are always better off just getting the best single card you can afford.
A GTX 560Ti would perform quite a bit better than a GTX 280.. The GTX 280 is outdated, the technology is 4+ years old.. It only supports DirectX 10 when DirectX 11 is the standard now, it uses older and slower GDDR3 memory vs. the newer, faster GDDR5 memory all the new cards.. It uses about twice as much power as a 650Ti...