First things first.....is the profile you're using now a *custom* profile that you made or the *default* one that came with the machine?
Assuming for a moment that you're using a custom profile, I doubt very much that changing the K generation to use more CMY and less K (less GCR effectively) will result in a more "colorful" RGB-to-CMYK conversion. Profiling applications are pretty darn good at MAINTAINING the same printed visual result REGARDLESS of what separation settings were used...that's how they're supposed to work
As far as RGB-to-CMYK, first thing would be to change the rendering intent from relative to perceptual...or visa-versa. While absolute and relative colorimetric renderings tend to be fairly consistent among different profiling apps, the perceptual rendering is a bit of a wild card....this is where you will most often see a difference among profiling apps, both good and bad. GENERALLY relative colorimetric + black point compensation is going to result in a more "saturated" RGB-to-CMYK conversion....but sometimes perceptual will surprise you.
If you're using ProfileMaker 5, you could also try some of the different perceptual renderings...Logo Classic, Chroma Plus and Colorful....and see what that does.
If you like, contact me privately and I'll take your measurement data and create a couple of profiles for you using i1Profiler and you can see how they work for you. I find i1Profiler to be a big improvement over ProfileMaker 5. Make sure you send me the *spectral* data file out of Measure Tool or ColorPort. Might also help to know what spectrophotometer you're using and what filtration (UVcut or no filter).
Lastly, just to set realistic expectations, depending on the available color gamut of you CMYK digital press, you can virtually ALWAYS expect to lose saturation when converting RGB-to-CMYK...just sort of a fact of life. It would help to know what digital press exactly you're talking about.....toner-based, liquid ink based, inkjet, what? And what RIP is this device using? There are lots of subtleties in the various color management engines used in digital press RIPs.
I'm also assuming that you're honoring embedded profiles in the RIP of this press so that it's picking up the correct embedded profile in the RGB images. Ignoring embedded profiles/tagged images could make a HUGE difference in the color rendering. It's not that big of a deal with most CMYK images (CMYK press profiles tend to more similar than different) but with RGB images, honoring profiles is a big deal.