I am still on the lookout for a sale on the Pioneer SP-BS22-LR, however I have tried the SMSL SA50 with some speakers I had lying around (source audio: computer) and the bass was pretty lacking compared to two other class d av receivers I tried them on. The speakers specs: impedance 8, 70watt, 60-20kHz, sensitivity 91dB. I've checked the polarity of the connections several times. Is it time for a subwoofer (with the Pioneers in mind)?