It supports any vga card that uses PCi-E slot, and supports all current AM3+ CPUs.
It does support overclocking, but its overclocking ability is decent. At the same price range, you can find the Gigabyte ga-970a-ud3 with much better power design.
it has two pci-e slots running at x16/x4 mode whereas the msi G46 has two pci-e slots running at x8/x8 dual mode which is much better and O.C ing with MSI is like a breeze