Thanks for all the replies so far. My inclination at this time is to go with one VTF-15H II with the thought of adding another (or more) if necessary. My room is pretty large and bass friendly. I've never really had an issue with standing waves and actually integrated one Martin Logan sub with some monitors several years ago with no problems. Since the CW IV does very well on it's own, I really need something with high output at lower frequencies. Hopefully I will get lucky and one is all I need.
Still thinking, but this is the way I'm leaning.
Oz