I bought the MM6501's and Infinty Kappa 60.9cs at the same time, hooked them up to my kicker zx350.4 amp , and wow these MM's blew the Kappa's away!Apples and oranges. Twice as loud, much cleaner, better highs & mids, after a month while the MM kept banging the infinty kappa's both fizzled out .
(Note one of the MM 6.5 drivers failed after about a month or two , polk replaced no questions asked. I just payed shipping to the company. Infinty is sending back tweeters as we speak but im ordering a 2nd set of these today)