CZ: The CZ75B is a great gun, along with the new P07 and both are well within your price range. They can double as a great plinking gun or for full-sized carry. Both feature cocked and locked operation, along with a DA/SA operation. P07 is polymer and the 75B is steel, if that makes any difference. The P07 is obviously lighter of course.
HK: You'll have to do some serious searching to find a good used HK under 600, but check out the USP series or a P2000 or perhaps a P30. All are difficult to find under 600, but I see more used USPs under 600 more than the others.
All three feature a lightning-fast mag release by the trigger guard. However, only the USP and USP compact models can be carried cocked and locked, if you prefer that mode of operation, and neither the P2000 nor the P30 feature external thumb safeties. The P30 and P2000 are more ergonomic than the USP though. Only the P30 has a standard Picatinny rail though and the USP and P2000 both have proprietary HK rails unfortunately. You CAN get an adapter, but it's just more money down the chute. All 3 are tack-drivers and amazingly reliable.
If you are buying the gun for range time primarily, you can't go wrong with a nine. It's cheaper and you get more range time in the long run. Plus, it can double as a carry/home defense weapon in a pinch.
You really can't go wrong with any of the choices above...