Well really it is the chipset that determined if it is a AM2 or AM2+, not how many watts processor it could run. AMD and Nvidia 700 series chipsets are AM2+. Up to 2000/4000 HT and PCIe 2.0.
Plus there is alot of AM2 boards that support 125W processors. The FX 62/ X2 6000 and X2 6400 were 125W. Like I said how many watts processor the board can run has nothing to do with if its a AM2 or AM2+
Some of the early AM2+ boards didnt have a good enough Power Phase set up and lower end mosfets and would burn up running a 125/140W Phenom. Most of them could even run a 9750 125W and even a 9850BE. But with the 9850BE they knew you were going to overclock and run the watts up higher, so they list them as unsupported.
If the board you have now doesnt support 125W then the 2 new AM2+ Phenom II will not run on it. They are 125W too. The AM3 that comes out later, from what I have read are 95W so there is a chance a lowerend AM2+ board will run them, but with DDR2 memory.
From what I have heard no AM2 board is going to get a Phenom II bios update. Only AM2+ boards.