for sure going for a high sulfate water. using the bru'n water pale ale profile.I think your blend is pretty good. I wouldn't mess around with other hop varieties - just up the amounts. The only exception is if you have something dank/piny like Chinook/Columbus/Simcoe. The varieties you're using are pretty citrus-forward, and Cascade can be pretty floral sometimes. A touch of pine on the palate might be a good counterpoint.
I do have more hops. I've got
(converted to ounces for the metrically disinclined)
6 oz centennial
6 oz citra
5 oz cascade
I've got some willamette and maybe a bit of magnum, and a few other odds and ends as well but I don't want to go crazy.
I'll up the whirlpool amounts. and the whirlpool time.