Can't find massive info on this, but I did find this from a pre-release infoguide:-
Socket-AM2, AM2+ and AM3: Backwards Compatibility - AMD Phenom II X4 940 & 920: A True Return to Competition
Socket-AM3 Phenom II parts will also work in Socket-AM2+ motherboards, the two are pin-compatible. When in an AM2+ board, these upcoming Phenom II processors will work in DDR2 mode, but when in an AM3 board they will work in DDR3 mode. How cool is that?
---------- Post added at 06:26 PM ---------- Previous post was at 06:22 PM ----------
Although I'm not seeing the exact CPU I listed in the compatibility list for your motherboard.
The Phenom IIs compatible with your mobo are:-
Socket Processor Processor Model sSpec/OPN# CPU Speed FSB/HT/BCLK Watts
AM3 AMD Phenom™ II X4 x945 HDX945WFK4DGI 3000Mhz 4000Mhz 95W
AM3 AMD Phenom™ II X4 x945 HDX945WFK4DGM 3000Mhz 4000Mhz 95W
AM3 AMD Phenom™ II X4 x925 HDX925WFK4DGM 2800Mhz 4000Mhz 95W
AM3 AMD Phenom™ II X4 x820 HDX820WFK4FGI 2800Mhz 4000Mhz 95W
AM3 AMD Phenom™ II X4 925 HDX925WFK4DGI 2800Mhz 3600Mhz 95W
AM3 AMD Phenom™ II X4 910e HD910EOCK4DGM 2600Mhz 4000Mhz 65W
AM3 AMD Phenom™ II X4 910 HDX910WFK4DGI 2600Mhz 3600Mhz 95W
AM3 AMD Phenom™ II X4 905e HD905EOCK4DGI 2500Mhz 4000Mhz 65W
AM3 AMD Phenom™ II X4 900e HD900EOCK4DGI 2400Mhz 4000Mhz 65W
AM3 AMD Phenom™ II X4 810 HDX810WFK4FGI 2600Mhz 4000Mhz 95W
AM3 AMD Phenom™ II X4 805 HDX805WFK4FGI 2500Mhz 4000Mhz 95W
The ones at the top are better (925 and the 945)
Basically, the Phenom II X4 945 is the best chip that will be compatible with your motherboard. I'm not seeing too many of these on eBay though. have a look and see what you can find from the above supporting models, remembering that the higher up this list they are the better (In theory!)
Oh and finally, if you haven't already, you may need to update your BIOS to support AM3 chips on an AM2+ socket.