Everything will fit on that board of yours, don't sweat it 🙂 though don't go expecting a massive upgrade path, especially regarding the CPU...
It looks like this:
ASUS M5A78L-M LX MOTHERBOARD, AMD 760G/SB710, DDR3, AUDIO, VGA, D-SUB, PCI-E, G-LAN, CROSSFIREX, MATX, S. AM3 / AM3+
$127
Intel Athlon II X3 450 BOX PROCESSOR, S. AM3, 3.2GHZ, 1.5MB CACHE, TRIPLE CORE
$186
PC-10666 MEMORY, 4 GB, Corsair Vengeance, 991769, DDR3 1333MHZ
$45
PCI-E VTX3D AMD Radeon HD 6770 GRAPHICS CARD, 1GB DDR5, D-SUB, DVI, HDMI, HDTV
$241
430W POWER SUPPLY, CORSAIR CX SERIES V2, COR-CMPSU-430CXV2EU, ATX2 V.2.3, 120MM FAN
$117
TOTAL: $715
www.newegg.comI went with a single 4GB stick of RAM just so you actually have an option to upgrade later. 🙂