Good for you. I love my eMac, though Final Cut finally outgrew it.
Hint: google "screen spanning doctor"
It is an excellent applescript that unlocks the video card's ability to dual display (not mirror). I have had it enabled since the beginning and the extra 19" monitor is a real godsend. Good luck!
P.S. I think OSX requires a minimum of 500Mhz. I dont think It'll even run Open Firmware 1.25Mhz system. 😀