Zane:
I gess I did not express myself right, I do not intend to edit on it, that would be insane, only converting AVCHD video files from SDHC cards to AppleProRes by loading SD card on an USB reader and putting APR files on an external disc. I will only use FCP to be able to convert the files by log and transfer. The process will be very slow but I don’t care it will be a back up of the SDHC cards.
None of the reasons you argue are against it. I do exactly the same when preparing to edit on my Imac, the difference is processor speed, ram memory and graphics memory. I do not need neither firewire nor thunderbolt, files can be imported and converted via USB.
Imac 27 Quad 2.93, 8GB Ram, 1GB Graphics, FW800 external + Raid