Very few speakers that are used as mains are magnetically shielded. Usually on centers a shielded. If you like the sound of the speakers then they'll be fine. Now you need to realize if you plan to buy a center channel that it will be next to impossible to find one that sounds similar (timbre matched) to your mains. This bothers some people more than others.
In my experiance, magnetic shielding is only an issue with direct view monitors, where the magnetic field in close proximity to the tube might interfere with the electron guns. In the obvious case of front projection, this is not a problem. Also, the guns tend to be buried in the bottom center of most RPTVs, so that also should not yield problems. In short, if the speakers you wish to use are placed next to the cabinet and no distortions are present in the convergenece grid (I would be suprised if there were any), you should be fine.
I think it bothers most people only if the center is brighter than the fronts.Most of the center speakers i've heard are a bit different and softer than main speakers maybe to make the dialogues more intelligible.
Thanks for the response.As for the LX44 i would like to know if it is better to buy old models or try new ones.Someone told me that value for money is an important point here, for that same price i would get only a mid end speakers if i buy new ones.