I'm in the market for a new heat source, and decided to go with a ZC unit. My current fireplace uses an 8" pipe. Trying to keep the initial investment as low as possible, I'd like to avoid installing a liner. So, my question is: What ZC high Eff. units use an 8 inch pipe. So far, I've found the Quadrafire 7100 uses an 8" inch pipe. Anyone know of others? Thanks.