Bookshelf speakers on a bookshelf?

I'm in a bit of a bind when it comes to speaker placement. I'm cobbling together a system for a friend, but the only place she has to put the speakers is in a bookshelf (stand-mounting is absolutely not an option, nor is floor-standing speakers). It's a 10' x 12' home office, and she'll be listening from her desk. The speakers can be placed in a bookshelf at ear-height.

I'm aware that bookshelf placement will kill the soundstage, but alas, such is life.

I've purchased a Linn Classik integrated/cd player for her (used, thank you Audiogon!). It has 75 watts into 4 ohms.

I'm thinking that speakers with front-firing ports would be best, but I'm open to all suggestions.

The other consideration is frequency response. I'm definitely intersted in speakers that go low - below 50 hz - (e.g., Silverline, rear-firing port). The Classik, however, has tone controls, and I could possibly use them boost the bass a bit. My price range is about $500 - $800, used.
All your thoughts and comments are welcome.
Thanks for your help.
Steve