If you've always admired the beautiful English double guns, but can't budget the $25,000 or more that even the plainest of these costs, you might want to look at a Spanish gun- an engraved gun like this AyA sidelock 20 gauge can often be found for as little as $4,000, and plainer box locks for even less. The gun pictured belongs to a friend of mine, who sold me his previous gun 15 years ago when he found this gun fit him better.
I think he paid about $3,000 at the time, which is certainly a bargain for a hand fitted, hand engraved gun in a custom fitted leather case. But there are a still lot of deal out there to be had.
Light doubles are just about perfect for upland game hunting, which is what we mainly do around here. Barrels are chocked open and improved cylinder, which makes them perfect for 10-30 yard shots (though I've dropped birds at 40). The short swing length and light weight make it easy to bring the gun up quickly at a fast moving pheasant or partridge. Light loads are the rule- 3/4 or 7/8oz of plated #6 pellets in a 20 is the perfect load for pheasant at close range.
If you're not pass shooting at ducks and geese there's little reason to carry a heavy auto or pump loaded with 12ga 2-3/4" or 3" magnums. You may have read that British shooters typically use 12 gauge guns for upland shooting, and that's true, but many of those guns- particularly the older ones- have 2-1/2" chambers and are loaded to 1oz or less; their upland 12ga. loads are pretty close to our 20ga. loads.