I've used semi-autos, pump, side-by-side, and over-and-under shotguns for trap. Here's what I've found from shooting each kind of gun:

- There are trap ranges where people really want to see open actions. Some of the shooters will not like pump and semi-auto guns, because they cannot tell at a glance, that the gun is safe. With break-action guns (side-by-side and O/U), you can tell without looking too closely that the gun cannot fire. Some ranges may insist that you have a chamber flag in a pump or semi-auto when you come off the line.

- Likewise, some trap ranges may with a semi-auto, insist that your gun control putting empties out onto the shooter on your right side. I got polite, but strong, encouragement to "do something" about my semi-auto field shotgun ejecting empties into the lane next to me when I used to shoot it in trap.

- You can control the ejection issue with a pump by tilting the gun to the right or catching the hull as you eject it with your right hand - or by shooting a bottom-ejecting pump action gun like an Ithaca Model 37.

- Pump guns require you to be pretty quick if you're shooting doubles.

- Pump or semi-auto guns have the downside that you have only one barrel, so only one choke, which can be an issue when you shoot doubles.  I like having two chokes on the side-by-sides and over/under shotguns I use - and typically, I'm shooting a "modified" and an "improved modified" or "modified" and "full" choke on my double-barrel guns.

- I like buying old American side-by-side shotguns and giving them a bit of TLC. There used to be the "economical" lines of American shotgun makers - eg, Fox Sterlingworth, Parker Vulcan, etc. These guns had the same action, the same barrels, etc as the highly embellished Fox and Parker guns, but without the embellishment that costs thousands of dollars. I've purchased Sterlingworth and Vulcan guns in good shape that were safe to shoot in the $600 to $750 range.

- Years ago, I purchased a Browning "Liege" shotgun - this was their gun between the Superposed (which is now a collector's item) and the Citori. The Liege was an inexpensive (in its day) O/U gun with fixed chokes. Today, I see the same gun that I bought 10 years ago for $600 is now selling for $1500 and up. The nice thing about the Liege I really like is that it has a mechanical trigger. Many modern guns like the Citori have an inertia trigger, which I don't like.

- The old SxS guns tend to have double triggers, which I like just fine. One thing that will make an old American gun less expensive is if it doesn't have ejectors, and has only lifters. This means that when you open the gun, you have to pull the spent shell from the chamber; this will be lifted about 1/4" up and out of the chamber. 

This is actually favored on trap ranges, and you will wear a bag on your waist to put your empties into while you're on the line. When you show up with a break gun that has lifters, the old trap shooters might smile at you before you fire your first shot. Some guys (and gals) really, really, really get bent out shape by shells being ejected into their lane.

My preferred trap guns today are the Browning Liege, and a Fox Sterlingworth I have with which I can hit everything that gets launched, with ease. The downside of the Sterlingworth is that it is under-bore, and the barrels get very hot after 25 rapid rounds. They get hot enough to seriously burn me if I'm shooting 50 fast rounds in doubles. This is pretty common in the older American SxS guns that were first made in the days of felt wads in shotgun ammo. 

Another possibility in a new gun to consider is the Winchester SXP Trap. These are a pump gun in your price range, and they have screw-in chokes, a chromed bore/chamber, and a Monte Carlo stock.  I was impressed by this offering from Winchester/FN today. It's not the Model 12, but it felt like a very nice pump gun.