I have made a few enlargements(direct optical c-prints) of some 645 Ektar 100 negs. Here's some examples of what can be achieved:

notes:
Pentax 645NII w/ 80-160mm zoom lens
Ektar 100, exposed @ 80ASA(next time I'll be using ASA50 for more shadow detail)
Processed (normal) @ IconLA in Kodak chemistry
Printed to Fuji Crystal Archive(Freestyle's re-branded stuff), processed in Fuji chems in a Colex RA-4 processor(local photo center has a full wet lab)
no contrast or color control masks have been employed, just straight prints

I've also included a contact sheet from another roll showing the saturation possible with this film

-Dan

EDIT: It seems the uploads have lost some of their "punch" color-wise, as the yellow of the car is VERY yellow. Of course, this representation might be affected by your monitor's brightness level. But you get an idea. Also the .jpeg conversion seems to have cut into the sky(top left, 1st picture) showing some banding/artifacting not present in the optical print itself of course