What's the differences in the older power supplies with ATX12V vs the new ATX 12V v2.31 ? Is there any reason I'd want to purchase the newer one just cause it has the new v2.31 label ? Such as what I'm really saying is (other than just wanting to know to know..) "Will the newer ones help something run better than the older ones?" I'm assuming the older ones will get the job done ?
ATX 12V indicates that the PSU is ATX v2.x compliant, the changes beween version 2.0 and 2.31 are very minor and dont actually affect anything, the requirements about how stable and clean the DC outputs must be have not changed. ATX 2.3 was passed March 2007, and its most significant addition was the removal of the 240VA per rail limit allowing for single rail PSUs.
Honestly, the differences between ATX 2.0 and ATX 2.3 are so insignificant that it didnt actually effect how PSUs were designed, if you have the connectors you need and your unit is working fine now, dont worry about what ATX version it is.