Re: RG500 and RG700 collection?
Well he already has the RG765, so he's got the hard one out of the way there LOL!
I'd look for a '92-93 RG770 with direct mount pickups. You could also look for an RG770DX that had a clear pickguard and maple fretboard. RG760's are great guitars and really easy to find. RG750's are probably the most rare of the regular production 700 Series, but still not overly difficult to find.
If you really want to get picky, there is an RG770FM that had a flame maple veneer top.
One other guitar you could try to get is an RG1200.