I've been following the AM3+ Zambezi CPU's, the high-performance Bulldozer's, and can say that you can go ahead and purchase a natively compatible AM3+ motherboard. I suggest, and currently use, the ASUS Sabertooth 990FX AM3+ AMD 990FX
as it is designed for those CPU's and come with the newer 990FX chipset which allows for both Crossfire and SLI. I got that board, a cheap Phenom II X4 955 and are going to wait for the FX-8130P to come out. Since you already have an AM3 CPU and DDR3 RAM, you are most of the way there already.
Though you can update to the Phenom II X6, it isn't suggested given how soon the new CPU's are to coming out and that the X6's are going to be end-of-life in a few months. It doesn't make much sense to go forward with the Phenom II X6 update, get a CPU that is about $100 or so, you won't be throwing money into a dying socket/CPU line.
Edited by DJBPace07, 16 June 2011 - 06:12 PM.