Hi Dave,
the DB1+ and TB2+ share an important factor with the IB2 and CB6.... they have the same designer!
They are voiced using the same criteria and will be fine for use in a multi channel system.
TheTB2+ would probably be the better choice as it's more efficient, has a higher handling capacity than the DB1+ and should be more able to keep pace with your IB1 and CB6.
Regards
Tom Barron @ PMC