One suggestion in case anyone else follows in your footsteps would possibly be to re-encode the h.264 or the prores files to animation. You could relink the footage and keep limping along. Any amount of animation footage will be much larger than the prores footage, but that may be the price one would have to pay.
In the end I think you did the right thing by upgrading, that g4 isn't getting any faster! Congrats on your new toys!
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you down with FCP?
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