another example of the difference between the old factory stuff and the new:
I had 944 "cup" style 16 inch wheels w/ 50 series Toyo's on my 1980 928 Euro S.
the wheels are lighter than the OEM disc wheels. (probably a pound or two lighter than OEM 928 disc wheels)
I upgraded to the following:
19x8 Carrera S 997 et57mm w/ Toyo Proxes T1-R 235/35/19
19x11 Carrera S 997 et67mm w/ Toyo Proxes T1-R 315/25/19
net weight loss was 44 pounds!
More traction (on DE course), lighter weight, and they look great.
If you're going to make a switch, go late model. You're handling will improve and you'll cut some weight.
Not quite as expensive/exotic as modular/multi piece wheels, but it is an easy improvement.