If you don't care for the look and just want praticality then a single flouresent would be the ticket especially the newer ones which are much more efficent.
Sticking with the MR16s then you could replace them with 20 or 30W lamps but look for IRC or Xenon types. The Xenon ones have very long lifetimes while the IRC ones burn brighter for the same energy but don't last as long.
LED has been mentioned this will be very energy friendly but expensive to purchase good quality fittings and drivers. I would suggest 3, 6, or
9W units. They are very bright but only over a narrow beam width and hence do not give the same effect. Cool white is the brightest with warm white having a lot less output.
Do you have any other lighting in the kitchen that could supplement the reduction of wattage in the downlighters.
A nice effect is to wash the ceiling with flouresents mounted on top of the wall cabinets. Great task lighting with few shadows.
My two pennith