I was in the same boat about a year ago. I now have generally gone the Parker reproduction route (20ga and 28ga), but I do have one sidelock a Grulla 216RL. It is a 6 3/4 pound 12 ga with 28" barrels (IC/M).
If I had to keep just one gun that would be the one without a doubt. Great quality and an absolute joy to shoot, it makes the ideal upland game gun and an all around shooter for any kind of clays. I found one in like new condition for $6000, but they generally run around $7,000 to $7,500.
Check out the book "Spanish Best" by Terry Weiland.
