Phono stage for newbie...

I am currently using a rega P7 TT with a Dynavector 20X-H (high output MM) cartridge. My preamp (Rotel RC-1082)has an onboard phono pre that sounds good. I have never experienced a separate phono pre so I have no idea where to start. My budget would be $500 - 700. Will this get me a phono pre that would sonically better the Rotel?
Try a tube phono stage. Pro-ject Tube Box /SE, or maybe a kit like a Bottlehead Seduction or Hagerman Bugle.
I would second the Tube Box. I've got one I'm listening to right now. Perhaps not the highest-fi, but a solid performer. Very smooth. It definately won't leave you hanging, and they're cheap.

btw, I have a Rotel 1072 pre-amp that I was using the p-stage in when I first got back into vinyl - do yourself a favor and get an external stage. The Rotel unit isn't up to snuff. You'll be amazed at the difference.
Tube BOX SE just got a very good rating from HIFICRITIC, which does not take ads. Much better than the Graham Slee Revelation + Elevator EXP which was rated at 26 points or the PS Audio which was less than that while the PRO-JEC was 49 points, so it is a real bargain. I am a VPI dealer and I think I will carry then for my customers who don't have phono stages.
I'm currently using a Rega P9 and Lyra cartridge with the Jolida JD-9a tube phono stage. I've had it 1-2 years and it's a real keeper. There's a recent review of it at as well. They sell new for about $450, well within your budget.
PS Audio GCPH is on sale for $695 shipped @ MusicDirect. I just reacquired one after having sold mine a few months ago with sellers regret. It is an outstanding unit that will not disappoint. Very quiet, accurate, versatile.
I have a VPI Scout with a Dynavector 20 (Special Edition 1.0 mv) and a Simaudio Moon LP 0.5 which retails at Music Direct for about $500. I have limited experience in this area but this phono preamp was recommneded to me by a person with many years experience and I am very pleased with the sound of my analog system. It is a solid state system.