im guessing they are 4 ohm subs... your best bet will be to wire them in stereo... if you run them mono at 8 ohms, you'll only be putting 90 watts to BOTH speakers.

what I really suggest is a new amp... a 50x2 amp will not drive a pair of subs very well... find a mono amp, then wire the subs parallel, to run the amp at 2 ohms... doubling the 4ohm power.