Rotel 1520 or separate phono stage?

I recently purchased a Rega RP3 with a sumiko blue point 2 cartridge. I have this connected to a Rotel 1520 integrated amp with PSB T55 speakers. I am now trying to figure out whether I should get a phono preamp and how much would I have to spend in order to get one that will outperform the phono stage that is built into the Rotel. I've researched the sub-$500 preamps but don't know enough about the specifications listed to know whether this would be an improvement over my Rotel. Any help/suggestions are greatly appreciated.