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If you are on a budget I would get a iMac G5.
The 17 inch model can be had for $1299, even cheaper if you can get EDU discount. Even a eMac will do videoediting very well, and its only $799..
You will also need an additional 512MB RAM sick, shouldn't cost more than $80-$100.

Depending on how much video you'll edit (and how much music you have), might consider to get a larger HD. A new HD is easy to install in the iMac (it's often cheaper to replace it yourself than make apple upgrade it for you)
 
I am in the same point as the topic starter.

Since I have a G3 upgraded to a G4 at this point, I am scrapping my project of building a G4 Quicksilver (in parts) and am going to buy a G5 Dual 2.0 for my next computer.

I am reading about the Tiger OS, which is mostly vented in the G5 direction, and I am excited to give it a try on a G5.

I am sure I will finish my Quicksiver project, since I alredy have a brand new Case (surpluss never used or had anything installed in it), Motherboard, and Power supply. I will just wait on it, and buy the fastest DP G4 Upgrade card I can find in a few months or so.
 
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