You didn't say what height the Warne rings are, but another option is an extended rail, like the GG&G scout rail, the RRA extended rail, one of the YHM, etc. These work well and give you lots of flexibility with medium rings, but they do add extra points of connection where you can get shifts or looseness.
If you want sturdy, simple, and inexpensive, the Armalite one-piece is a good bet, but the semi-QR thumbscrews do stick out a bit, and it's got a centerline of 1.25", which is a little low for some people. They're $90 new, or $50-75 on EE. You could also watch Armalite's 12 Days of sales going on now to see if they put the one-piece up.
The LaRue is considered the best. If you need QR levers and a bit more height, it's well worth it, and it holds its value well if you ever want to get rid of it. Like everywhere, if you want the best, you pay extra.