A friend of mine is attempting to "prestige" an old RG 550.
She's filing the ends of the frets to make them smoother/rounder, going to strip the back of the neck and put a satin finsih on it, so on and so forth . . . however, I don't think it's going to end up being nearly the same as a true top end RG or Jem, you can only "spit and polish" something to a point, and at that point the limitations of what you started with are going to stop you from making things any better.
When she's finished I'll let you know my opinion. My Godmother's son works at a music store and I have played quite a few Jems, sadly I can't afford one, but that's neither here nor there.
I'll let you know how I feel it compares. Keep in mind, just MY opinion, means nothing. :P
Oh, and this "old" RG 550 is old/new stock. It's a brand new guitar that sat in the back of a store for a few years. I've checked it out and the neck is just about perfect, we've already put a set of Evolutions (and an old Fender USA standard single coil) in there, so it sounds great. The maple is a little bright, but that's to be expected. She just didn't like how the sides of the fretboard felt when she slid her hand over the neck. The frets bit, she played on a Jem and loved it, but like me can't afford one, and being a woodworker by trade (she makes wonderful clock bodies, faces and wood figures) she said, "I can make my guitar feel like that." so she's going to give it a run.