you heard the midbass was weak? running what? Rainbow Soundline standard mids are some of the more pronounced midbass range 2way drivers around comparing them to much more pricey sets. Kickbass is a step above that in the 80-220 range while maintaing superb midrange up to the 2500hz cxover point.
I'm running 8's for mids and would say the Rainbow Kickbass drivers are FAR from weak. They are comparable to the Focal K2p mids, Scanspeak Rev's in the usable midbass performance IMO- and people rave about those. But the Scan rev'sare not quite give you the same midrange clarity as the other two IMO. The standard midbass drivers are not 'weak' by any means- they are detailed, accurate, punchy...if you desire the more robust, exxagerated midbass punch out of the same size driver thats what the Kickbass is suited for. All these 'super' 6" subs out there people are bonering about (xxx, ed ) have unacceptable upper midrange capability and I even personally thought their midbass was weak IB.
Apparently people dont think too much about the things that make or break a particular drivers purpose in car (other than properly installing them) Like what rearstage (subs/power) are you trying to keep up with?Power? System Integration is key.
I say running a pair of 12's w/ 1kw+ rms....there aren't many 6.5's out there that would please me unless sealed and have the subs attenuated to hell to blend in.
I know people running the Ed 6's as subs, not midbass. Not quite the type of driver you want in a 2way application. There are lots of variables, application/integration included. IMO the more 'sub -like' performance you expect from your midbass, the closer you are leaning towards a 3way setup.