Alternative to my P3ESR

I have a pair of Harbeth P3ESR in my desktop set-up, powered by a Primaluna Dialogue Premium with KT150 power tubes. I love the imaging and mids, especially in acoustic music, but I miss the mid-bass. I have a Rel T5, but it's helping the lowest bass, not giving that mid-bass thump I am looking for. I tried a few solid-state amps but missed the tube sound - and they both felt fatiguing in comparison. 

Any suggestions on an alternative standmount at a similar price that I should consider for near-field listening? I'm about four feet from the speakers, they're three feet from the back wall.