Best bookshelf speakers

I have been down this road more than once. Opinions from others are all over the place. Their recommendations may be well founded but there is a very important factor to consider..............Some speakers sound fantastic connected to some electronics and horrible when connected to others. If there is any chance for you to audition speakers connected to your, or similar, electronics then do it.I have had speakers that sounded great connected to one system and another...not good.My 2cents.

I agree with @Bache, you are asking for the "sky is the limit" in terms of features but "low ceiling budget." Something has to give.. However, since i am popping off about your situation no one yet has mentioned Elac Debut 6.2 (which i am listening to as i type) or the Elac Uni-Fi-Ub5. I can tell you the Debut are worth every bit of the $250.00 asking price.. I recently connected PS Stellar M700’s amps and the speakers are responding pretty damn well. However, I have a pair of Burchart S400’s coming though so these will be stored or sold in the next few weeks, (maybe). 

Dynaudio Emits

I would recommend the KEFs. You'll be hard-pressed to find bookshelf speakers in that price range that image better and they provide fantastic detail. However, as decent as the KEFs are with regard to bass output and extension, there are better options in that regard. You can find RBH 41-SE or better yet 61-SE speakers on the used market in your price range. They are just about as detailed as KEFs with slightly less "edge" vs. the KEFs. And their aluminum woofers output way more bass than drivers that size should. But if your primary focus is bass output and extension, I've never heard speakers that can best Hsu Research CCB-8s unless you opt for something much larger (be it a monitor or a tower.) Those also have a coaxial driver, so like the KEFs, you should get superior imaging if you set them up properly. (The Hsu's are at or beyond your declared budget new, but you have 30 days to try and return them if you end up not liking them.)

A MTM design is likely your best chance at getting big sound from a bookshelf on a modest budget.