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No, M-CR60 is not underpowered
Let me explain, Your TSx220B is BS and your Marantz M-CR603 's output rating is 60W/channel @ 6ohms
And I am using Marantz PM6004 (45w/channel @8ohms), with Polk TSx330T, a FS, with ease.
If My PM6004 can drive a floorstander without any issue, Marantz M-CR603 will be able to drive TSx220B without any issue.
Take a look @ the power consumption of both the equipments...
Marantz MCR603 is around 50W consumption where as PM 6004 is 150W...You can pair the speakers with MCR603, But make sure you don't push them too much on the volume...