Is 8 Core P.Mac worth it?

I'm thinking of changing the 2 proc. G5 Power Mac and upgrading to an Intel Mac Pro. I've read the reviews on Macworld etc. and the 8-way system does not seem to offer a significant advantage for most tasks over the 4way (All gains seem to be 10% or less I think). So.....

• What apps CAN take advantage of these extra procs today? (I mainly use Aperture, Final Cut and Logic - hobby only not pro basis).
• Anyone got any views on whether 2 4-way systems might be a better investment? (Leaving the 2nd system to act as a slave node to process in the background)
• What is the best graphics card option for the above? (I plan to drive 2 * 30'' at most).

Thanks.

netdog said:

If you do a lot of video rendering, the 8-core should do it in nearly half the time of the 4-core (provided that you also have enough RAM).

Click to expand...

Do you mean as in exporting to H.264? that type of thing. I do output to 720p H.264 for viewing on Apple TV etc. But tend to leave that type of thing overnight. Nice if it happens faster, but it is the real time manipulation stuff that I am mainly interested in the performance difference.

Thanks for the input. all helps.