I have three .45s -- a Ruger P90, a Springfield GI 1911, and a Kimber Tactical Ultra II -- but as you're looking for something less than $650, the Kimber's out. The P90 was about $420 plus tax, and the GI 1911 even less, at $390 plus tax. I'd always heard good things about the Ruger P-series pistols, and I have nothing but good things to say about the P90 -- it's bulky, to be sure, but shoots very well, it's built like a tank and eats anything I feed it.
As for the 1911, of course people's mileage will vary, but so far my experience with Springfield -- the company and the pistol itself -- have been great. When I got the 1911, I noticed about once every 100 rounds it'd get a stovepipe jam, and this was pretty consistent. After about 400 rounds, I wrote the good folks at the Springfield Custom Shop and told them what it was doing, and they recommended I send it in. Not quite four weeks later, I got it back, with a new extractor, and it's run flawlessly ever since.