OK for that price range there is some economy type O/U's available, but like always you get what you pay for. If I only had the $700 to play with I would look real hard for a used Browning, Beretta, or Ruger. To get one of these new start around $1000 depending on models.
For someone who wants the gun for skeet and sporting clays, spend the extra money for a durable gun that will last and has good warrenty work available.
I mean a round of 100 sporting clays is gonna set you back about $30-$40 depending where your at plus shells, you have up to $60 in a one day shoot. A good gun is a small investment compared to the cost of shooting. It's all relative of how and where to spend the money. A 870 for $200 and spend the rest on shells.?