To port or not to port

Hiya,

I have a dedicated 2 channel music only set up. (no HT) and currently have a pair of PSB Synchrony One B bookshelfs. I really like the speakers but sometimes percussive bass gets boomy and bass guitar has a resonant, for lack of a better term, droning quality to it. I feel the rear ports are the culprit. I've moved the speakers away from the wall in increments but it still remains. I've used every bass management crossover option on my pre-amp to no avail. PSB does not recommend stuffing the ports.

I'm thinking of going with a sealed design since I have a Rythmik sub to handle the low frequencies and a Parasound A21 amp to handle the lower sensitivity of a sealed box.

In the $2-3000 dollar range I've only come across 2 models.
The Vapor Audio Sundog and two from ATC, the SCM11 and SCM 19.

Would a sealed box "tighten things up" in the low end? And does anyone know of any other manufacturers making a sealed bookshelf?

Thanks.