Hi paulzoom,
I did a graphics card upgrade about 2 months ago and am very happy
with the results. I posted a similar question to yours and got
great advice here.
I am on a Dual 2.3 GHz PPC G5. I upgraded to the ATI RADEON X1900
from the Nivdia GeForce 6600 card that came with the machine. I
also added RAM, going from 2.5 GB to 4.5 GB.
The added RAM was to improve the speed of Photoshop. It made a
really noticable difference with PS speed; thus the combined
upgrade of RAM and graphics card has turned this into a great
machine.
My experience with Aperture is that the X1900 has improved
performance from what I consider "poor", to very good. Aperture
launches much faster, the HUD comes up practically as soon as I
click on the icon and all HUD adjustments are completed quickly.
With the X1900, there is almost no time delay between the time I
adjust the slider and the visible adjustment on the image onscreen.
Cycling through images in Aperture is faster. I'm happy with the
improvement in speed. One thing though, I would not condider
Aperture a "lightening fast" program. Aperture offers a lot of
things that I need/like in a program, but "super fast speed" is not
one of them (at least not with the configuration I am using).
Having said that, the performance of Aperture has improved greatly
with the new graphics card. After using the X1900, I would not
consider using a slower graphics card with Aperture.
If you upgrade your graphics card, make certain the card is for a
dual core PCI EXPRESS bus. There are a couple of different cards
available.
I don't know anything about the speed difference between the PPC
and the Intel Macs, so can't reply to that part of your question.
regards,
Londongal