Cap'n, while you make a good point on identifying the target, I disagree on the usefullnes of night sights. I can think of lots of scenarios where a civilian might need to fire on a subject that was not currently lit up with a flashlight (including potentially
after ID ing them with the light). Fact is, flashlights and night sights are both great tools, and each has their use. (I know, it's arfcom... get both!)
As to choosing a 1911 in your price range, there are quite a few good options. Among the best
may be
a used Colt 70 series (or a new 80 series) or a Springfield Armory Mil SPec (which would leave a few dollars for sights or other customization).
As another thought, I bet you could come up with just a tad more money. I bought my SA PX9109L for just a little over $700. It comes with trituium night sights, extended ambi safety, a beavertail GS, a carry bevel treatmnt and a nice parkerized finish. Here's a pic (sorry about the SAA clone in the pic, had the shot lying around from another post).