Getting ready to buy a set of bookshelf speakers and wondering what the impact of laying the speakers on their sides on a bookshelf.  Will this significantly mess up the sound quality?  I have built in bookshelves that sit on top of larger base cabinets (
see pic). 
I am considering the Monoprice K-Bas speakers.  Any others I should consider?   I am budgeting about $500 each speaker.
Will also be buying a couple subwoofers and a slim center channel to place in the room as well.
Thanks in advance!