1. PianoTeq advanced features allow you to set up several channels for several speakers. I think you should try this, maybe positioning the PianoTeq mics in the same place as your speakers (for a start).
2. I think small subwoofers can add a lot of the feeling of lower frequencies that 4" speakers can't reach. A few tricks:
- Set volume by ear so they blend in with other speakers. Then drop volume a bit more so you feel them rather than hear them. The effect should be very subtle.
- Positioning subs is really tough but the "crawl around the room method" works fine and is easy.
- If you get two subs then positioning becomes much less critical so this is really the way to go; there is a good white paper by Harmon, the US audio company regarding this. Small subs are very cheap on craigslist as people are not into home theatre or audio anymore.