Heresy's might be a good choice, but I suspect you will not get as much bass as you might like. I've owned both Heresy's and TC50's. One direction you might try if you are runing tubes is a Galante Rhapsody. It is a bit on the larger side of a monitor, much like the Heresy. In a small room they will produce what I perceive to be more bass than either TC50's or Heresys. Actual response figures don't necessarily reflect that with the Rhapsody's going down to 50hz before dropping off - they are rear-ported and I have them near corners (where else in a room that small) which may be reinforcing the bass. I have had all three pairs of speakers in the same small room a bit smaller than yours, and the Rhapsody's do best and are more refined than either Heresy or TC50. If you try the Heresy route there are many mods to do on those speakers that will improve their sound. Plenty written already about that subject in the archives here, and by the "fanatics" over on the klipsch site. They're great little speakers, but I have not found them to put out much low bass. I'd agree to raise them up and tilt them up by just a bit. I tried them on low stands, but that really kills the bass. Cornwalls would certainly be a good choice for bass, but are much larger than other options, and may even overload a small room. Forte II's may do the job as well. Chorus II's may also, but again, I'd be concerned about overloading the room at that point. I'd still point at the Rhapsody for a more refined sound, albeit not as fast as Klipsch horn options.
Good luck.
Marco
Good luck.
Marco