IPSC, as run by USPSA in the United States, has four divisions for semi-autos:
1. Production, which is basically double-action autos with no more than 10 round mags. There is no major/minor power factor distinction: everyone just has to make minor (125PF). I see Glocks and SIGs moft often in this class.
2. Limited, no optical sights, must be .40/10mm caliber or larger to make major (165PF). No capacity limit, except mags must fit in 140mm box. The most competitive guns in this class are high-capacity, double-stack guns in .40SW, and most are based on either the SV/STI design or the Para-Ordnance.
Alternatively, you can shoot a .40SW Glock in this class and use your hi-cap mags.
3. Limited-10, Same rules as Limited, but only 10 round mags allowed. A single-stack 1911 can be competitive in this division at the club level, as long as you have 10-round mags.
4. Open, anything goes. I think there's a 160mm magazine length restriction.
You probably cannot get a Open gun for nuder $1200. If you want to stay with a single-stack 1911, you'll be shooting in Limited-10 division. The criteria for a such a gun is not really anything special: it has to be near 100% reliable, and it has to be accurate enough to hit an IPSC "head shot" (6"?) at 30 yards max.
I have been shooting L-10 with my Dan Wesson Patriot for over a year. It had some teething problems but once those were sorted out, it's been 100% reliable.
You may be able to find a used double-stack 1911 for Limited class for $1200 if you look around. A Para is probably more likely in that price range than an STI/SV.