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


Lately, I've been craving deeper, tighter bass. I'd like to hear some ideas for replacing my Silverline 17.5 monitors. Is this a stupid question, due to inherent limitations of driver size imposed by typical bookshelf dimensions, or might I actually do better with another speaker? Amplification is Wells Audio 150 watt SS Majestic integrated. Source is aging Jolida JD100 tubed cdp (in new year, I plan to replace this with another SS cdp or a transport/standalone dac combo). Thanks ! 
stuartk
Not even one or two really small subs like REL T Zero or the slighter larger SVS SB1000? You can tuck them away in two corners of the room and equalize the boost from the room corner.
For me, the best small high quality speaker with quite decent low frequency extension would be the Harbeth M30.1, but I have obviously not heard all that is on the market. See: http://www.theabsolutesound.com/articles/harbeth-monitor-301-loudspeaker/
willemj: In fact, the SVS is one I've definitely considered. But as I've said, when I ask salesmen about the fussiness of sub placement, they always hedge their responses, which makes me hesitate. I did read the Harbeth review. . . interesting! Will have to research whether any Northern CA audio dealers stock them. Thanks for the suggestion! 
I faced similar domestic restrictions and opted for a B&W PV1d to match our minimalist modern interior.
I think the concerns about placement and integration of subwoofers are to be taken seriously, but they can be overcome without too much difficulty. The problem is room modes, the resonances at critical dimensions of the room. With the traditional unequalized single (big) sub, finding the right spot and creating good integration is indeed hard. The solution is simple and twofold: multiple subs (two small ones is usually enough) and room equalization. Two small subs will smoothen the response because the peaks and dips from one sub’s location will not be at the same frequencies as from the other sub’s location. In practical terms, as the DSpeaker Antimode engineer told me, just push two little subs into two adjacent corners of the room, benefit from corner boost to get rid of dips/nulls, and use equalization to reduce the peaks. Using the very affordable DSpeaker Antimode 8033 is dead easy: it is automatic, and takes maybe half an hour, including reading the manual. The result is quite dramatic, changing bass response from woolly and ’slow’ to tight and ’fast’. The Antimode will also equalize the response of just one sub (as in my case) but only for a more restricted listening area. That area gets significantly larger with two. So next on my purchase list is a second PV1d, but that is another story.
I would think that in a medium size room like yours, two small subs in the room’s corners would be visually more attractive than, for example, larger floorstanders (that often also introduce bass response problems). As for SVS, they have a generous return policy, so you are not risking much. Listening to subs and comparing them in a dealer's demo room is next to meaningless, because you are listening to the character of the room rather than the sub.