Two powered subs with bookshelf speakers or two floor-standing speakers?

It may depend on what you define as bookshelf. A 7” or 8” woofer can go low enough to make the sub truly a subwoofer. A 4” or 5” woofer usually cannot, so the “sub” is really covering a range into the midbass where its presence is more discernible and thereby harder to blend in. The other issue is placement. Not every room affords you the option of putting speakers where they can sound their best.  Having a sub can either ease or worsen this problem…

I’ve often considering going from two stand mounts, two subs (current setup) to two floor standers, two subs but I hesitate because my current setup sounds absolutely amazing as is and I also like having one of the two subs as a near field sub, just to the left of my listening position. Works great in my room this way. The other sub is in the corner behind my right channel stand mount speaker. My point is that bass is sometimes better dispersed in the room if you can play around with the sub placement rather than having it tethered to you speaker as it is in a floor standing speaker.  

You’ll never use your bookshelves again if you get a good pair of floorstanders. My Tekton Pendragons give you deep solid lows...smooth mids and slightly rolled off highs but detailed. Very musical and $2500 pr. Get the 7 tweeter array option.

I had a number of very good bookshelf speakers (B&W 805D, Harbeth 30.2) and subwoofers (REL, SVS) in different rooms. Sound was very good but not even close to floor standers I now use (Wilson, Spatial Audio). As others stated above, integrating subs with bookshelfs can be difficult. I am convinced that using floor standers is much better option.

-GAR

Aesthetic considerations (room decor circa 1915) and small size 15' x 15' necessitated use of small bookshelf B&W 805's and subs REL T7/x's to blend/hide the speakers in the background.  RELs in the corners, B&W's literally on bookshelves.  Less than ideal, however toeing the speakers and fine tuning bass volume and crossover has yielded a very nice soundstage and a very musical sounding room.  My brother who has Monitor floor standing speakers used my room as the bench mark for his HiFi system.  So yes it can be done to good results.