welcome to team akg....i recently upgrade to the 460's from the 391's. the 391's were great for me, and i am not disappointed by the 460's.
i run then ck61 & 63's flat. the good thing about these mics is that if and when you upgrade to the 480's, you can use the same caps.
i have some specs on the 460's that i got from the prior owner (3 specs pages) that i can email you if you like.
i am not sure what the difference is between the 460's and 480's...i think the 480's are transformerless. the 460's seem to be cooveted by orchestral tapers. jim williams at
www.audioupgrades.com can modify them, and make them transformerless, and some say when that mod is done to the 460's that they are superior to the 480's...but i have no experience or comparison to back that up. search this and the OLD oade board for "460" and you will find a ton of material/discussion of this subject.
good luck, and have a grateful day
chris k