Please suggest bookshelf with best bass response under $4000 pr.

You have some really nice monitors.  If u like the rest of their sound I'd highly recommend adding a sub with some integration hardware to help them blend.  Specifically, I'd get a used DSpeaker antimode 2.0 for about 500 bucks and an SVS SB1000 used for about $300 and see how that works out.  My bet is you'll be in music heaven (both available here now), but if not u can sell the sub and processor for little or no loss.  Short of going this route, I'd look for a used pair of Joseph Audio Pulsars, but I'd try the sub route first because you'll get the benefit of lower bass that can be so transformational to a system properly done.  Best of luck. 

Ive also heard great things about the Elac AS-61 monitors but they might just suck every amp of current from your amplifier in order to sound as they should.
The Calibre mentioned earlier is also very impressive both esthetically and sonically but they’ll push you way out of your budget when considering the cost of the stands required to match their quality.
Just as an aside, the monitors that keep blowing me away everyime I see/hear them at the NYC Audio Show are Sonner speakers designed and made in Massachusetts and only one model in their lineup. If you close your eyes you think they are huge floor-standers with incredible imaging and a wide and deep soundstage. Just boggles the mind how it could make this sound out of a two way pretty small monitors.The problem is they cost $10K and $12K including the stands. Probably others heard them as well at the show.

Yes, the Sooner monitors are absolutely killer. I fell quite hard for them when I first heard them but the $7K asking price gave me pause. They have some of the most beautiful, expressive, and airy highs I've heard. So much so that at first I thought the mids and bass were lacking a bit, but it was just that I was hearing, for the first time, some excellent rendering from the upper mids and highs. A great choice if you can afford them.

As for the power hungry Elacs (85db) I have no problem driving my 85db Clearwave Duet 6 monitors to lease breaking levels with my 90 watt Marantz integrated. 😃 That Well Audio integrated should be able to handle them.

All the best,
Nonoise

My harbeth c7es3 have great bass response.   Way better than the 30.1 imo.   Just a fantastic speaker all around!   Plus it matches up with most amps.  I do prefer a solid state preamp with them.  

I owned a couple pairs of Totem Mani-2’s and if you have enough power from a good SS amp, you will get very good bass. I had a 200 watt Classe CA-200 amp at the time and they needed more power. I teamed them up with the McIntosh 1000 watt monos and they sounded amazing.