1. That is fine for occasional work but too slow for regualr use - go dual core.
2. No it doesnt.
3. Small speed increase in speed, maybe 10% - better to raid for safety not speed.
4. No better - actually my ratpor b marks quicker than my mates scsi 320 (shock)
5. Most pro editors can use 4 cores. Cecck with vendors if in doubt.
6. Rendering hdv ( i presume you mean hdv when you say hd?) is much much slower than SD - 4 times slower i would estimate. Precisely why I dont bother with hdv.
7. Not really.

That'll be £100 consultation fee please ! (bargain)

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I have two prejudices - I am anti HDV for consumer camcorders, and I eat mooks who claim to be pro wedding vidders and ask dumb questions.

www.zaskarfilms.com You tube channel 'zaskarfilms'
JVC DV5001e (big cam), Sony PC6E (tiny cam), Vinten pro5, PAG light, SM58, Sony ECM50, Sony C-76, 0.5x convertors for sony, Rode video mic, Vegas 7.