Yup
One line for each signal gives a much clearer picture than what both composite and S-video can supply.
According to the Mini-DVI pinout there are all the signals I need (as far as I know, these are the R, G and B lines, H-sync and V-sync), but no web-search has shown me any such adapter which is why I'm not taking it for granted that it'll work. Perhaps the sync rates out from the iMac aren't compatible with a TV?
(it's a previous generation iMac -the one before the newly introduced ones; they have mini-display ports as far as I know).
By the way: which "flavor" of the Mini-DVI connector does the mentioned iMac have? I've heard there are several kinds (DVI-I, DVI-D etc.).