I think Theo's points of break in and cabling are valid.
It also may be that the 500's are bringing out more of the speakers nuances than the Ma7000 did. It might be controlling the lower frequencies better and therefore it sounds darker. If that's the case then repositioning the speakers may help (along with other tweaks) to get them to open up and be better balanced.
When you change more than one thing in a system you really have to do a lot of experimenting to sort through it all.
I use to own the Mac 602. Loved it but it didn't play well with ALL the speakers I put on it.
It also may be that the 500's are bringing out more of the speakers nuances than the Ma7000 did. It might be controlling the lower frequencies better and therefore it sounds darker. If that's the case then repositioning the speakers may help (along with other tweaks) to get them to open up and be better balanced.
When you change more than one thing in a system you really have to do a lot of experimenting to sort through it all.
I use to own the Mac 602. Loved it but it didn't play well with ALL the speakers I put on it.