It's a long time since I gave up shooting, so I'm not in touch with things, most any old school dealer will be OK, you should get a very nice gun for that money, think about what chokes you want for clays, and if you intend to go rough shooting.
Some modern guns have screw in chokes so you can alter them to suit your requirements on the day, might be worth considering if your new to the sport as you can tailor your spread and reach to the shoot.
If your joining a club, which is a good idea for clay shooting, go along, talk to the old and intermediate lads, and get some feedback, maybe find someone to accompany you when you go to buy.
That will help on a second hand gun, and they will be able to help find a gun that fits you, though stocks can be shortened or extended, you want to be settled with the thing in general.