Yes, that is a significant upgrade.
They will work just fine with your Rotel.
There are subwoofers that will produce more OUTPUT for the money, lots of them, but for sound quality, K10s are priced just right and they still provide a good boom. K10s are really nice sounding subs.
I actually have one paired with some Dynaudio Audience 42s on the turntables. I really enjoy it.
-Chad