Besides the SP and White Onyx in 20 gauge, Beretta make a nice alloy framed variant that weighs less than 6 lbs.
My old SKB is a great candidate here, but at 6 lbs,12 oz it's on the heavy side for an uplander. Still, one with 26" barrels and choked IC/Mod would be a keeper.
In the last year or so I've got to try a few shots with Franchi and Cesar Guerneri 20 gauge O/Us. Check those out also.