Datacolor User to User Support Group.

On some occasions I need good quality slides made from digital files
and I can't afford to pay a lot of money for them, so I use service
companies that will do them for approximately $2.50 each.  I have
tried several companies, and some of these companies seem to give
reproducable results, but I have found none that give me slides that
have the colors and luminosity just right (The closest I have come is
Slides.com.). I have my monitor profiled with the Spyder2Pro system,
and the files print out reasonably correctly (on an Epson 2200
printer) with the "canned" profiles, and even better with profiles I
prepare using PrintFix Pro. From this evidence I presume that I am
making properly color-managed files.  I can adjust the files so that
the slides come out somewhat better by using (usually substantial)
adjustments in Photoshop of levels, curves and/or color balance, but
it is hard to get everything just right. 

Is there any way, preferably using the Colorvision products, but any
way that works, of creating a good profile that I can apply to the
files before I send them to the service company to have the slides
made that will make the resultant slides better?

Thanks for any help you can give.

Bailey