Unfortunately, you can't just toss a couple Celestion F12-X200 drivers into any old 2x12 and expect it sound good. Every driver pairs with it's cabinet to achieve certain design goals... it's a system that works together. Everything from cabinet materials, internal volume, porting, bracing, and acoustic fill all contribute to how a cabinet will sound.
Hopefully, Celestion will release some suggested ported/non-ported cabinet volume specs.