Slow response times are not an issue with plasma. However, with LCDs, it is.
From what I can tell from my basic research so far( and this is by no means to be accepted with the same level of validity as my audio advice, as with this video technology, I am only referring to higher level sources of information, and I distinctly lack the founding knowledge base in video to have a highly probable level of certainty of anything ), the main issue with a plasma is that apparently the brightness change in the plasma cells reduces exponentially, in reverse, and relative to image brightness: when you first use the unit, for about the first 100 or so hours(though overall, the curve is still flattening out until about 2000 hours, there after being even less change after that point), the brightness reduces much faster than any other time(after this period, the brightness change flattens out), and if you have static images on for long periods that are white or near white(being maximum brightness), it may reduce the brightness from that area of pixels enough to leave a slight darkened area. If you do not use static images for long period in the first 100 or so hours, it is of popular opinion among experts that you are not likely to experience easily visible burn-in. Many people use plasmas for game play. Refer to avsforum.com in the flat panel display area. The most likely issue to occur is reversible, and that is that the gas particles can polarize over the static image sections; but this is easily corrected by displaying alternating noise(no channel static, for example) or using a bright screen wipe function(on a DVD, or some televisions have this function built in). Few ever experience this burn-in phenomenon. Perhaps if you played one game, and only one game, almost all of the time, you may have a highly probable situation where you can expect some visible burn-in on still bright graphics that are always on-screen. I also have a plasma, and I have every intention of using it to play games when I get a hold of a PS3. According to experts and most manufacturers, the plasma should not be any more subject to burn-in as compared to a CRT.
As for specific recommendations, I would recommend the Panasonic TH-42Px60U, because it measures very accurate color (without calibration, but a few basic settings need to be changed in the menu) and has superb black levels, as well as being produced by a manufacturer known for reliable, high quality plasma displays. The unit can be found for under your listed price range from online reputable dealers.
-Chris