You must be using some really bad film to have it too grainy at 100 ISO. Here is a photo of an ugly garbage thing. Guess the ISO!
No cheating now...
Fuji Superia 400. Yes, it has grain, when I view it at 100%, which yields 21 megapixel files. But who judges grain by pixel peeping? If I were pixel peeping using my scanner, I can peep out the grain in Velvia 50, and that stuff is practically grainless! I think you'd be better served by film if you used a trusted brand and lowered your expectations slightly. Film will not be as nearly grainless as 100 ISO dSLR images -- that's life. Negative film will, however, have very generous dynamic range, far exceeding what most dSLRs can squeeze out (except maybe the Fuji S5, but that's built specifically for dynamic range).
Also, please consider the quality of your scanner before judging the exposure and colour of your film. C41 film is very difficult to overexpose. About the only portions of my shots that are truly "clipped" are specular highlights reflecting the sun.
If you require more saturation, I recommend Kodak Ektar 100, exposed at box speed (or rated at 80 when using an external light meter, to account for light loss in lens), or slide films. Velvia 50 or 100 come to mind, but they tend to make people's faces too red or orange. If you're taking images of people, use Velvia 100F. If you want toned down, but still saturated, colours, and you may have people in your shots, use Provia 100F.