Boondoggle-
I love my 2 GP2's, but for you, I would steer clear of the GP2 for two reasons: 1) you describe yourself as "rev-dominant"....2) in the past year, your Hextreme was strong enough to handle the most oil you saw.
That being said, I think the Desert Heat is an excellent place to start. After that, I would go for a Slash as your oil ball. The Slash is generally very smooth and should be able to even out over/under situations for you, which would probably be magnified due to your rev-dominant game.
Finally, I'd go with either a Heat, an Xception, or an Arsenal Angular, as any of the three should fit in between the Slash and the Desert Heat pretty well, and they would all give you good length and a strong backend. The Xception will give you the most possible length and the strongest backend, followed by the Arsenal Angular, then the Heat, in my experiences with each ball.
Good luck with your purchases, and if you need any help laying out your equipment, give us some specifics as far as PAP, speed, rev rate, etc...and I'm sure one of our Track pro shop gurus can fix you up!
--------------------
Jeff Voght
PBA Eastern Region Member