The FX 8300 is an OEM chip @ 95w
Fx 8320E is likely a retail version of it @ 95 w
Both are considered 95w chips because their non turbo clock speed is slower then the Fx 8320
They are all relatively the same, any of them running at say 4.5 Ghz if able to do so, on all 8 cores will be equal in speed. It will just be a matter of how good the silicon is, which will determine what voltage will be necessary to run it there. Johan recently picked up a sweetheart Fx 8320 that runs on really low voltage. If I recall correctly it does 5.0 at around 1.42 Cpu V. To give you an example to compare it to, my Fx 8350 which was purchased when first available for retail, needs 1.46875 to run 4.7 stable on water. It seems as if they are binning the high leakage chips for the Fx 9370/9590 series chips and keeping the low leakage ones for the 8xxx series ones.