The center is like the most important speaker (and subs) for the HT experience so unless you are in love with the 8000F, I would reconsider. Neither of the Klipsch centers are particularly good and I tested the RC64 iii, the 504c and the old RC7.
If you want a BIG step up, grab the Revel C208 center while still on sale. That one is leagues above anything from Klipsch and at the current price, I dont see anything that can approach it.
Then you can either get the Revel towers or wait for a sale on the JBL 590s which work surprisingly good with the Revel center.
