We are running a DL320-G4 with a 2.8 or 2.9 GHz processor and it is running 5.1, however if you want to go to 6.0, you'll have to have the 3.4. Luckily I think it's just a processor upgrade so it should be a straight-forward migration from 4.x. We started at 5.0 and upgraded with no issues, however you're looking at a different upgrade experience coming from 4.x.
BTW, good luck getting a DL320 if you're going that route, the G4's are no longer in production and the G5's are not out yet!
These are the paths to get to each CCX logs through CLI. They may be helpful if you are having issues accessing RTMT or downloading logs through it.
If you want to download them you have to prefix "file get " and you can add one of the options (re...