I have purchased 2 sets of magnesium Group 4 wheels from Marvic, the wheels are a work of art and Marvic are wonderful people to deal with. The current US$/Euro FX rate would make them a bargain price too!
Note that Marvic only produces the rears in the Group 4 race version of 14" wide, they work well with the 345/35 PIrelli tire and fill the flares a little more than the 13" road version and those came originally with a spacer anyway.
I recently replied to a question on the e-mail regarding wheel weights,
10" 2 slot Campagnolo 19lbs
10" 10 spoke Marvic repro Campi 14lbs
13" 10 spoke OEM Campagnolo 16.5lbs
14" 10 spoke Marvic repro Campi 17lbs
Looks like Roin have added to their De Tomaso range, I don't have comparative weights for their aluminum wheels.