How big is your room? I tried out my 170's in the front when I got them as surrounds just out of curiosity and they sure sounded great. My room is too big however and I need the extra oomph of the 340's for the front. I would absolutely recommend all 170's if your room isn't overly large. Just for reference, my room is 14'x19' with a 12' cathedral ceiling and is open on two sides to the rest of the house.
If you look in the reviews area for a review by Nicholas Mosher he has an all 170 system setup and loves it.
Darren
There's no place like 127.0.0.1