Hello Craig,
Currently I have a four speaker system. The right and left are a matched pair of 1986 Heresy II's on slant stands (birch w/ cane grills).
My center (using PK's design of a mixing box and mono amp) is a "homemade" Klipsch hybrid. It has a ElectroVoice T-35 (K-77) tweeter, An ElectroVoice M-10 mid (same diaphram as the T-35...voice matched and horn size about he same as the K700), and a Klipsch K-1008-V woofer all run off of a E-2 Heresy crossover. I had to build this center because it sits under my TV and the Heresys totally trashed the screen with the big woofer magnet. No Academy has tried to force it's way into my house as of yet...I keep hoping!
Since I have a small room (no more additions possible) I am using a Yamaha YST-45 subwoofer. Not large but adds nicely to the total mix. It is shielded and sits beside the center under the TV.
We are planning on building a new house and in the designs I have made room and plans for a true 7.1 Klipsch home entertainment system. Till then I must say I am very pleased with the mix-and-match I now have. I have always (at least 30 years) loved the Heritage sound. Gets no better than that!