I have owned both .45's and 9mm's in 1911's. I much prefer a 9mm for a multitude of reasons; less recoil making it more enjoyable to shoot, cheaper ammo, good self defense ammo available, can be found in just about any configuration possible. I understand there are .45 1911 purists and I respect that but that does not diminish the fact that the 1911 in 9mm is a great pistol.....it is. I currently have three 9mm 1911's and all have been great with no problems. It was mentioned earlier what about a SS 9mm 1911, take a look at the S&W 1911 9mm Pro Series. Excellent pistol and great trigger right out of the box, a good condition used one can be found for the price point you are wanting to spend. The best bargain for the money, it's hard to beat a Rock Island Tactical 1911 9mm, mine has been flawless. I have never owned an STI but I have read many good things about their pistols, one thing though, their frames are Rock Island frames.
Hmmmm, must be something to the Rock Islands for them to do that. The Springfield RO is a very good pistol. I owned a Springfield Mil-Spec SS, it gave no problems but the trigger was horrible out of the box. After I did a trigger job it was a pleasure to shoot. For the money, the Ruger is fantastic. If it weren't for the fact that I made a nice profit on mine I would still have it. Truly American made, Tactical version, good trigger, just and overall nice 1911. Look around, there are several options available and I'm sure you will find what your looking for. Hope that helps. Good Luck.