Are there any bookshelf speakers that sound good on a bookshelf?

I had a pair of Focal Aria 906's that I used in a true bookshelf environment and was quite happy with the sound.  They are way below your budgeted investment level, but, are very pleasing to the ear.  I used them with a pair of smaller subs placed elsewhere in the room, but honestly they could produce plenty of bass by themselves.

I was fortunate enough that the shelving units upon which they sat were pretty close to my ear level, and, they are front ported so I had minimal concerns with the rear wall placement.  The nice thing about them as well is that they had quite a lot of sound disbursement and required little to no toe-in for proper sound at my listening position, another plus for them since there was limited space in the shelf for them to be rotated. 

Tune Tot by Wilson made for the very purpose that you are referencing ...

Vandersteen VLR CT.

Had a pair for about two years now and really like them. (Paired with Ayre integrated.) They are especially good at low to mid volume listening (about 85dB and below.) Room is 20x14. In fact, I plan to go Vandersteen when I step up to floor-standers, based on my experience with the VLRs. Exceptional.

Proac Response 2 or 2R.   Great speaker, with a front port.   In my experience, anything with a rear port needs a foam plug when located in a bookshelf, and then the bass response rolls off, and then life becomes a little less enjoyable.  I’m sure there are exceptions, but that’s my experience.  Of course imaging will suffer with a bookshelf location, but if this is a “real world” situation not involving a dedicated room, then I have had the best luck with the Response 2’s.   

Save lots of money try the KEF LS50, awesome speaker!!!