It's been said that the ppc board is a lot better technology that x86 boards.
Careful with those statements...
"Registered SDRAM ECC DIMM" support are not unique to PPC world.
Refer to
http://www.creativecow.net/articles/hawes_tyler/amd_mps/athlonmp_760mp_full.html
1) I need to know specifics about the type of ram I need to purchase.
I recall, they required the registered types. Not to sure about buffered or un-buffered types.