There's a real Ithaca 16 Ga SxS in my local shop for $300. Color case still 95%+. That gun, though not new, is better than anything new for anywhere near the money.
Otherwise, get a CZ (Huglu) SxS 20 Ga. It's a genuine bargain in that it's truly a great gun, but not too expensive. It's beautiful in appearance, flawless in construction, and swings like an old English gun.
Don't get a cheap O/U. The Spartan and Stoeger are overweight clunkers that swing like pickaxes. I'd consider a Mossberg (nice gun made by Khan), but for a few bucks more I'd get the CZ SxS instead, because it's a really nice gun at any price.