Alternative to my P3ESR

I doubt you will find anything "better" than the Harbeths under $2k. Different, of course.

lack of mid bass is likely from something like a desk reflection causing the bass null...try adjusting your boundaries if you can. The Harbeth's should be strong down to around 70hz. 

Try raising the crossover point of the REL T5...that will help fill in the hole.

If you require a high subwoofer crossover point....especially above 80hz, the REL T-Zero will do better in that 80-130hz range. 

A measurement mic will really show you what's going on. You may just be a mid bass head ;-) 

Some great insights and suggestions in here! My P3esrs sound better driven by my Wyred4sound 100w class D amp than they did with my sugden a21se sig (which sounds sublime over the Atalante 3 in my main system - those speakers are probably too big for your application though). Maybe sell the speakers and put the proceeds toward one of the P3 XD models and/or buy a more powerful SS amp to try. Something about the sound you get out of that diminutive P3 format that would make me reluctant to switch from that model altogether!

Selling my P3esr’s was one of the few times I’ve regretted selling my gear. It’s hard to describe but there’s something special about the sound these little guys produce. My suggestion is to buy a beefy SS amp. The P3esr’s will scale further. 

Thank you for all the comments and advice. Speaker placement and subwoofer integration has done a lot to help. I moved them closer together and a bit closer to the back wall. I set the sub crossover closer to 80hz and increased the volume a little. The sub integration will take a bit of fiddling about but that's part of the fun. There is so much I love about the sound of these Harbeths, and they image so well, I am going to stick with them for now. I tried a NAD 218 and a Bryston 2B before, but I found them both fatiguing compared to my Primaluna in triode mode.