Be aware of one thing: Quicktime for Linux won't read any of the movies you download from the internet. Quicktime is a wrapper for many different kinds of compression formats. What you knew as "Quicktime 4", "Quicktime 5", "Quicktime 6", are really different distributions of compression formats. The codecs we support are mainly uncompressed.
have you used Quicktime 4 Linux? cause i think it's more a creator/writer than a reader. i don't think i can use it to read already compressed quicktime files such as what i download.
Mplayer plays quicktimes perfectly, and is certainly not a pay service (crossover is though). I highly reccomend it. Also, VLC will do quicktime, but I think you have to dl those codecs seprately.
Just a side note: there is a mozilla plugin for mplayer that may make the web stuff work just fine too. I havent used it for awile, but the last time I used it, it worked well. Here is a link.