Is the box sealed or ported?
If it is ported, I wouldn't go much further than the recommended 175 watts RMS rating. Maybe 200 watts maximium.
If its sealed, it should handle 250 watts.
IF YOU DO GO OVER THE RECOMMENDED RMS WATTAGE...ADJUST YOUR GAINS ACCORDINGLY!
Here is a good write-up on adjusting your gains. With properly adjusted gains, slightly over-powering your subwoofer should be a problem.
From the reviews (most of them crappy in nature and VERY bias) on
www.polkaudio.com and a few others, these don't seem to suffer from the blowing voice coils like the Polk MOMO subs used to have in the past when they first came out.
EDIT: Forgot to say that your amp should be just fine for those subwoofers. Unless you plan on upgrading to bigger/better subwoofers in the future, just keep your amp.