Lack Of Low End

[relayer]

I have just upgraded my stereo system from an NAD 7175 to Rotel RC971 pre and an RB981 power amp.The NAD had substantialy more deep low end. I have Siefert Research Paragon Speakers and the low end from the NAD made it uneccessary to add a SUB. Now It seems I desperetely need a SUB. The NAD seemed much smoother. Am I missing something here?