Here's another option-- Abu Garcia has introduced a new center drag reel system. One is built in Sweden and costs a lot; it's the Suveran. It's heavy being all metal, but it is great. They just introduced a lighter model, the Center Drag, that I was fortunate enough to test on chinook in the Elk River in SW Oregon.
I don't think I would have a spinning reel without a center drag system if I was fishing for big, hard-running fish. Not only are the drag washers two to four times larger than those on front-drag reels (and a whole lot larger than those on rear drag reels), they are easy to get to if you want to adjust the drag while playing a fish.
On this trip, we landed chinook up to 30 lbs on the reels with no problems.
I've also used the Suveran and turned a seal which grabbed my rockfish. The seal ran about 100 yards before stopping, and the drag had no faults or chatters. It equalled the drag on the best baitcasters.
If you're stuck on Shimano, that's one thing, they are good reels, but I would certainly look at the Center Drags before I buy.