Hello Ian
The processor(s) you mention I think is an AMD dual core speed 2.3GHz, 1MB (512KB each core) level 2 cache and 2MB level 3 cache.
It is made on the same core technology B3 as the 9x50 Phenom X4 (not Phenom II) processors except two cores instead of four.
I have seen this processor named as Athlon 64 X2 6500+, Phenom X2 6500+ or just Phenom 6500.
Processor naming can be confusing.
An upgrade from a dual core to a quad core processor can really increase the polyphony your computer can generate as Hauptwerk benefits very well from more processor cores.
Here is a list of processors supported by your motherboard GA-MA69G-S3H:
http://www.giga-byte.dk/products/mb/cpu ... 3h_10.html
It is a Danish site, but the list can be used anyway.
As you see some quad core Phenom and Phenom II processors are supported but not all.
The new generation Phenom II would be the better choice. The core technology is slightly improved and 45nm, the level 3 cache is 6MB (except two) and the power consumption is less at the same speed. On the list you can also see which BIOS version is needed to support a specific processor. If you need the BIOS to be updated, it shall be done before the processor is changed, and update it to the newest version.
You are welcome to ask again.
Best regards
Johannes