Most of Colt's 1911-pattern pistols are actually good guns. The company kind of crapped out in the mid-90s, but their newer stuff is supposed to be excellent. I own one, a Delta Elite, and am extremely happy with it. They tend to be more finicky with some kinds of ammo, but the worst case scenario to make them run perfectly is usually a $40 reliability job by a good gunsmith. But bear in mind that most 1911 pistols run really well box stock with most kinds of ammo; my Delta Elite certainly does. Normally you just need a new magazine for them to run right... Wilson Combat and Chip McCormick magazines are both excellent. Colt prices tend to be really high nowadays because of the trouble the company was (and kinda still is) in. Getting ANY Colt -- new or used -- for under $600 nowadays is a good deal from what I've seen. Don't worry too much about how "tight" your 1911 is... about 95% of the accuracy comes from the fit of the barrel, slide and bushing (more on that later).
Aftermarket gear? Most of it is gravy, but some of it will make your pistol more functional. If your trigger is plastic, having a aluminum match trigger fitted and a trigger job done to your pistol (nothing loony, just 4-5lbs and crisp) will make it easier to shoot well and doesn't cost that much. Next, if your sights are crappy like many 1911s, adding a set of better sights will be suprisingly helpful (I prefer Novak low profile, but they are kind of expensive and there are alot of other good ones). Night sights are a good idea if it is a self-defense weapon. If you have any feeding problems, get new magazines first, they are by far the #1 culprit in ALL semi-automatic pistols. Any feed issues that doesn't fix should be easily curable by a gunsmith for about $40. And finally, if you realize that your *pistol* (not you) needs more accuracy, have a Bar-Sto Target Match barrel fitted to your gun and your pistol will be able to shoot rings around almost anything out there. Kart and Jarvis barrels are supposed to be outstanding, too.
Hope that helps.