There are a few people I play against who use the 500T and all seem to really like it. I get the feeling its one of those rackets that is just a really good all-rounder.
But maybe you do just need to try a few strings. Personally, I quite like Silk. I use it without a dampener and it feels very comfortable with a goof feel to it.
"Tennis is just chess with balls."
Using: Dunlop Biomimetic 300