Just a note, in case you didn't know, the FPX is a catalytic unit, meaning you'll need to replace the cat (~$400) every 3-7 years they say, depending on how good the wood your burning is. On the upside, cat units are much easier to achieve secondary combustion, not that the quad isn't.
Both are built extremely well and will last a long time.
I kinda wonder how the FPX is so cheap installed, usally they are in the $7000 range, because they are more complicated to hook up with thier pos-pressure system, the prices I got for these were both very much the same installed, FPX being slightly more, in the $7k range.
That said, I personally do not buy into FPX posi-pressure system. I do not like the idea of taking cold outside for heating a home. Outside air kits for combustion air, yes, those work great, increase your efficiency and have no-ill effects. But the posi-pressure system FPX units have to pull outside air, circulate it around your firebox, and push it into the house, I don't like it. I know the marketing material says it'll create positive pressure so instead of a fire using air from your house creating negative pressure, FPX design pressurizes your house. Well, I think ithat creates 2 problems. The major of which is, you don't want a pressurized house. You want a balanced house. Because with pressurizing, then, you start to push warm heated air into and thru all the walls, door cracks, window crevices, etc, warm air condenses upon hitting cold air, so now you will have moisture in your walls and areas you don't want moisture. If you have an older drafty poorly insulated house, this effect will become very apparent. The 2nd issue is, your trying to heat 20degree outside air. Why not start with 70degree air and blow it around your firebox and back in. For combustion air, taking 20degree air and blowing it into a 1100+ degree firebox, is no consequence, the percent change isn't much different than using 70 degree air for combustion.
My neighbor has been burning a FPX in a log home for 8+ years now. He's got a very drafty home, and he in the process now of replacing some wood in and around the attic because it's rotted. There is no evidence of roof leaks or the like, and it's very difficult to prove the FPX posi-pressure system did it, but if I were a CSI, that'd be the first thing I would investigate as the culprit. Of course, he's never replaced his cat, I've seen it, it needs replaced, he refuses "It's fine!" he keeps telling me, "These are expensive!", he says. Smoke is usally coming out his chimney, so perhaps his burning methods are more of an issue, he tends to let his house swing alot, like 65-78, which isn't so good for moisture reasons also. SO I can't say it's the FPX, but, I just don't like the idea of pressurizing my home.
I'd investigate why the FPX is so cheap installed, did you quote you everything? Chimney system, posi-pressure system...all that, because it's not an easy install. Persnally, I'd hang my hat on the 7100, but that's just me!
Good luck, and post up pics of the retro-fit!
BTW, the 7100, with an optional add on (see their accessories page) can posi-pressure your house to, if you really buy into that solution.
