Bookshelf Recommendations

Agree with Jim (tomic601), Vandy 1s would be perfect in your 12x12 room. I'm using Vandy 2s in an almost 14x14 room, with treatment, they are setup 9" from front wall, 7' apart (tweeter to tweeter), no toe-in, and listening seated head position is 2' from rear wall. No bass boom.
Hope this helps,

Tom

Paradigm Signature S1 version 2 or 3

Rega RS1's.  do not get the newer RX1's.  disappointing. 

I use a set of pre-owned KEF LS-50s on stands in a 15 foot squared room with 9 foot ceiling and while they won't ever convince you that they are full range; they do what they do really well; highly detailed and enjoyable music that is fun to listen to without physically dominated the room (spouse acceptance factor).  Don't be too quick to dump your solid state amplifier, I am a devotee of tubed pre-amps with a CJ Act 2 and solid state amplifier power with a CJ 2500 A.  I've had tubed amps in the system and it is too "tubey", meaning soft, a little slow and somewhat muffled compared to the tubed pre-amp, solid state amp combination.

What speakers are you replacing? 

I also use a tube pre with a SS amp. A solid approach for many reasons. Not to say the only one.

A couple stand mount speakers I have heard you might consider:        Dynaudio X14, X18
   B&W CM5
Either could be bought used for~$700. 

The Vandy 1Cs may also serve you well.