I faced this dilemma many years ago, when there just weren't that many non-Colt 1911s around. The gun shop had an AMT Hardballer and a Colt Mk. IV sitting side-by-side. Other than a Randall or Llama (shudder), the AMT was the only alternative to the Colt. The Colt was about $100 more, and I just couldn't make myself part with the extra money.
Well, the AMT worked for a while and then just stopped, and the factory never could (or would) fix it. I sold it for a song (actually, just one chorus) and bought one of the first Glock 17s. I've had more Glocks, a few revolvers, and am currently tinkering with a Rock Island GI model 1911.
The Glocks are dead-nuts reliable, easy to work on, light to carry, completely rust-proof, and can take a serious beating. But I do enjoy shooting the 1911--it's hard to beat even a mediocre 1911 trigger.
And the other night I wondered what would have happened if I'd just ponied up the extra cash for that Colt all those years ago. I'd probably still have it, and never have had to spend all that cash on all those other guns. Spending more up front would have saved me far more money in the long run.
Even though I like my RIA, my advice is this: spend more money and get a Colt 1991 in .45 ACP. No Rock Island, no Kimber, no Ruger, no Springfield. And no 10mm.
And go easy on modifications. Spur hammer? Beavertail safety? Front cocking serrations? Meh. Good sights and a good trigger are the things you really need. The rest? Not so much. You're better off modifying yourself, with training and practice.
Don't just spend your $600. Make that $600, plus maybe another $300 or $400, last you the rest of your life.