Klipsch Forte IIIs vs. Heresy III with a sub

I have Forte IIIs but wifey thinks they are too big for our living room / 2 channel listening room.  Considering swapping for Heresy IIIs and adding a sub.  I like to get the really low frequency in stuff like Sylvan Esso but also want the sound of Klipsch for classic rock and jazz.

Three questions:

Will the Heresy IIIs sound as good as the Forte IIIs do now if I add the sub?
Will I be able to cross the sub over to match well with the Heresy's bass range?
Will a Sunfire 8" XTEQ sub work well with the Heresy IIIs?

Oddly, I just had a chance to hear a pair of Forte III. Their sound characteristics were completely different than what I get from my Heresy II's. The two speakers were not directly side by side, but at no time have my Heresy sounded like the Forte III in the sense that the Forte III have a boxy kind of rough, loose, hollow sound to them. IMO, the Forte doesn't sound as tight and controlled. For example, I compared the B&W 601 S3 to the 602 S3. The 602 is a slightly bigger cabinet and slightly larger bass driver. When I played Louis Armstrong and Ella Fitzgerald, the trumpet and voices clearly sounded better in the smaller 601 speaker. They sounded tighter, real and more controlled in the smaller 601 speaker. In the 602, the trumpet and voice were less coherent and less controlled. They sounded more loose. It was only while playing large classical orchestra where the larger 602 out shined the 601 overall because of the 602's larger sound stage and bass extension. I said hell with the Forte III's after that and have completely lost interest in them after hearing them last Friday. They sound nothing like my Heresy's and they don't sound as smooth and silky. I added a new 8" REL sub to my Heresy and dropped my jaw. It's like a wall of amazing sound.
It's kind of hard to get horns to sound "boxy", isn't it?
Boxy in the sense that it sounded more like a hollow box speaker. I’d describe it as a box without sound deadening. 
Klipsch is lo-fi these days. The old man made some good stuff once upon a time.