I took your advice and opted for the 3 Xantrex-GT3s, and was able to get the installer to split the difference (they were bound to Home Depot's pricings on fixed packages, but was willing to cover half the difference). I wanted to go with Home Depot mainly due to panel availability and aesthetics (black mono-crystaline 175W BP modules). The installer's willingness to be flexible cemented the deal.
Decision factors:
+ Xantrex-GT3 more compact, newer technology, builtin communications.
+ Installers seem to like Xantrex more due to ease of installs. Perhaps the better installation design tells of overall design?
+ 3 less expensive inverters easier to split into zones and replace than 2 more expensive ones.
Thanks for the wonderful resource that is this website and forum.
KTT