Hi S !
I do not know about HK 630-but I can tell you that unless your room is very large (ask Axiom C.S.!)you can not go past 0 on HK7300.My room is 24X14 and I never went past -5.The M80 play extremely loud at this level, it is more than a normal(sorry!)human being can hear without at least a partial hearing loss-in my opinion.And I did not even calibrate the system yet(I still do not know how to do it!).
Overall, the combination HK7300-M80-VP150-QS8 is fantastic!
Enjoy!
Regards,
Octavian