I'll echo the sentiments of those who mentioned Communic. Though I'm not a big fan (they just haven't clicked for me yet), I think they fit the bill perfectly and would be a nice addition.
Other bands that would make for good openers or two slot bands:
Degree Absolute - not sure if they're a live act
Kiuas - a perfect fit for ProgPower
Order of Nine - maybe more of a pre-party band, but a band who would sell a lot of discs after their appearance
Persuader - a #2 band that would be a lock to go over well
Pharaoh - an opener who might finally get some of the credit they deserve if they played PP
Zod