SPEAKERS, SPEAKERS AND MORE SPEAKERS.. BUT NEED BASS.?

Well for MY modest system I put away a pair of K.E.F. LS50 with two older passive subs filtered at 80 Hz by my receiver and powered by a secondary amp, replaced them with a pair of SVS Ultra Tower speakers that I snagged "almost new" for $1k and have been very happy with them at this stage of my system building. 

Lets shout about it!!

Another option that comes in well below your budget would be a set of the Canton Vento 890.2 from accessories for less.  I'm seriously considering a set myself. 

Regarding Duke's finding of reduced transparency as result of high-pass filtering of main speakers, if a 1st-order filter is sufficient, a simple passive one can be installed on the input jacks of the amp powering the speakers, just a single cap usually. His approach of instead making speakers that are built to handle the demands of a full-range signal ignores one of the major benefits of high-pass filtering---removing the low frequencies from not just the speaker, but also the amp driving them.

So here is what we know about the OP:

1) He listens to Jazz and Folk;
2) He may or may not have speakers since he hasn’t bothered to tell us what he has.
3) He likes bass, only cares about the bass, has told us nothing about what he prefers for other characteristics of a speaker.
4) He has a room, it is small, but who knows where his speakers are placed, where he sits, or if there are setup problems.
5) Any speakers with horns are out because as he puts it: " I have a small size room and no I do not want horns!! I am not a huge rock or pop genre listener... all I need is “ENOUGH BASS”".
6) He wants to spend less than $4000.

So given all the amazing information provided, I suggest the following:

1) Cerwin Vega SL-15- "large motor 15" woofer for punchy bass".
2) Polk S60 with "(3) 6.5” low distortion mica-reinforced polypropylene cones with four-layer voice coils for clean, clear bass, better linearity, and dynamic mid-range" and " Exclusive Polk Power Port technology for greater, more impactful bass".
3) Bic Venturi DV-84 with "Two 8" polymer active woofers, two 8" passive radiators".
4) Dayton Audio T652 with " Dual 6-1/2" woofers provide superb bass power and punch" . . . "for unobtrusive yet modern aesthetics and incredibly deep bass."

All of the above meet your stated criteria and should provide, as you put it “ENOUGH BASS”.

" happy listening....
Cheers"