Make sure you re-balance your speaker levels and sub level after hooking up the bookshelf speakers. Speakers have different efficiencies, and without doing this the new speakers could be too loud or too soft relative to your other speakers and sub.
Verify your sub crossover is what you expect, usually about 80Hz.
Also the Mirage M990 is a dipole design. Two 6.5" woofers, one forward firing 4" mid and 1" tweeter, and one rearward firing 4" mid and 1" tweeter.
ANY other unipole speaker, bookshelf or floor standing, will sound different from this. Not necessarily better or worse, but different. Be prepared for it.
Let us know the result.
