It really depends on your opinion what qualifies a certain version as being the best. You may have already found it but I wanted to pass along this link in hopes that it may help answer your question:
You may also want to check this link out as well as it will give you some insight on some of the 4.5 versions that are out there for the 8320 currently.
I'm sure you've already done quite a bit of research and know to stay away from some versions of the 4.5 as it will do more damage than good on your particular model. I hope this helps and best of luck to you.