It's kinda hard to beat your CZ75. I'd save a few extra pennies and get it a big brother. After a year of owning and shooting a CZ SP-01 Phantom I can unqualifiedly recommend that gun to anyone. I'm not sure how much they are going for used, but I'd still consider it.
I'd also stongly consider just about any 2nd or 3rd Gen Smith, and definitely a Walther P1. Used Beretta 92 can also be had around the OP's price range.