As JD mentioned, before I started sinking money into amps and a new receiver I would look at improving your speakers and sub. Money spent there will have a much greater impact then watts or a new receiver. The Klipsch is a good budget value sub, but not in the same league as those from SVS, Rthymik, PSA, RSL, HSU, Outlaw, Monoprice and others.
There is no perfect display, quit looking for faults and enjoy
LG OLED 65” B7 and 55” C8
Ascend's with RAAL, Love my PSA v1800 and a 7.2.4 speaker config, Oppo 203 and other stuff