Matt
Thanks for P.M
Indeed i did used too own 2 Storms that were replaced by Servo's (i now use 4 which i believe to be quite an experience by almost anyones standards)
Personally speaking i sit firmly in the camp that believes two sub's are better than one (for many reasons i am sure you are aware of).
So personally with your' predicament i would stick with two Storms over one Servo (others will doubtless disagree!!!) if your room is of a medium/large size.
That said as i and others have previously stated the Servo knocks the Rel into a cocked hat as regards sheer extension and spl's, IMHO the ONLY downsides to the Servo is (perhaps for some) physical size and that it isn't best suited to a small room (but that shouldn't be taken as an absolute negative it WILL perform in a small room, you will just have acoustic issues that you cannot counter due to size etc)
Steve.