The actual CD is 411 MB, but I have no idea what a compressed image would pair down to.
As for which system... the 400 MHz sounds great. It has to be much faster than my ThinkPad which is at 133 MHz. I can play Quicktime movies and Doom with out any problems (the only two apps where speed is actually a factor). The only problem with the Pentium II 400 is a possible problem with the keyboard settings (I'll go back through my documentation to see what the work around was), and may have only been a factor in the first generation of that processor. On my systems I went through and matched up cards with drivers I knew I had (like the display driver for the ThinkPad 760ED, which was why I have that model).
Also I'll go through and make screen shots of each set in the installation (I did this once for NEXTSTEP, but didn't for Rhapsody because I never thought that many people would be interested in it).