lack of rms power affect sq?

No, because if you are applying 75 watts per channel of clean power to a decent well installed component set, the volume will far surpass the range where SQ is the primary consideration.  At high volume levels, our ears go into protective mode.  Sound quality is appreciated at moderate volume when your ears aren't closing up to protect the eardrum.

The 170 watt RMS rating for the speakers indicates that they have been tested to achieve sound production at a lower freq than the typical mids-to-sub crossover point of 80 Hz (lower freqs take a substantially greater amount of power).  That doesn't mean that they sound good at 50 Hz, though;  the sub is supposed to sound good producing that freq range.  Just a few watts is all that is needed for maximum SQ. 

Listen to speakers first;  consider their ratings as an afterthought.  The 170 watt rating may be a clue that they will blend well with the sub by having a strong bass region, but listen to a few setups at the stereo shop before deciding.