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

Well, if you check the OP's 2nd post, he mentions studio monitors, hence the suggestion. I don't see a problem myself. 

I second the nomination of the Elac Adante AS-61 monitors. The first shipment will be coming in sometime around 11/16-11/20 and every week thereafter. I, myself, am waiting to hear them as I liked the floor standers. 

They're a there way design with a sealed box, something that you don't see much of with monitors. They vent via the passive bass radiator on  the front (the actual bass driver is situated behind it). You'd save $1.5K and just may like it.

Another one would be the Studio Electric M4 for around the same price as the Elacs and they, too, are a sealed design. I've yet to hear them but the chatter is they are very good. I'm lucky in that I can listen to both in my area. Try to audition before you commit.

All the best,
Nonoise

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