By your questions I think you need the services of a qualified lighting designer. Someone has to design the entire lighting system for the area not just point you to a track head or lamp. That someone may use a combination of lamp wattages and beam angles. Title 24 requires more than dimmers in the kitchen area. You must have 50% by wattage of high efficiency fixtures and this becomes a real challange in some kitchen designs.

You can use a 110V track system that use stems that can be purchased at different lengths, with pivots at the ceiling which will allow the track to hang parallel to the ground.
By using modulars components you can attach virtually any type of track head or even pendant fixtures to this track which will allow you the greatest flexibility considering your lay out. In as far as the dimmer goes this will be dependant upon the fixtures that are used on the track but should be a simple issue none the less.
Any knowlegable lighting sales person should be able to help you pick out the various parts that would be required for your installation.
Good luck
ken

Thanks, dim4fun and lighting ken, for your advice. I truly have been hanging out in lighting stores and online in order to learn as much as possible about this subject. I feel that I need some information in advance of approaching the lighting designers, in order to be able to analyze and judge what I'm going to be told.

Dim4fun, we've put as much under-cabinet and over-cabinet fluorescent lighting into this kitchen as we can fit; now we've got to use our remaining 50% wattage as efficiently as possible to illuminate the island. I believe that the sunroom portion of the room, which is well outside the work core, will qualify as an "other" space, so that the dimming option for incandescent lighting will apply there.

Ken, I've seen pictures of the systems you describe, where the entire track is suspended, as well as systems where it is the track heads that are on stems of different lengths.

Thanks again!