a light but strong rim is the dt swiss 4.1d.. ive hammered one on the front of my bike in switzerland for a month in the summer.. m aybe not very hardcore sounding but certainly worth a look.

i still wouldnt think 28 spokes will be an advantage in the long run as all the other measures your taking will shave the weight off but an extra four spokes will give a stronger wheel fot not much more weight