Digital BW, The Print

I'm not sure where to best ask this, but I think it's of interest to this group. I'm in the 
process of deciding whether to buy a new Mac. Photoshop is the most important 
application I run and my objective is to run it faster.

I have a Power Mac Dual 2.5 G5 at 10.4.10 and Photoshop CS2. A new machine would be a 
Mac Pro running CS3. Reviewing articles in MacWorld, I see that the time required to run 
their Photoshop Suite, "a set of scripted tasks ..." is:

Power Mac G5 Dual 2.7 GHz (two single cores) and CS2: 0.48 seconds
(8/10/2006 and 8/16/2006)

Mac Pro/2 dual core 3GHz Xeon (four cores) and CS3: 0.50 seconds
(6/6/07 and 7/19/07; the eight core version improves to 0.48)

Assuming that their Suite has not changed between articles (it is described identically and 
should be a constant to be able to compare apples to apples) I need to spend several 
thousand dollars to get to where I am now, plus new features of CS3. (I'm ignoring the 
difference between my Dual 2.5 and the Dual 2.7 used in the tests.)

MacWorld talks about applications needing to by written to take advantage of multiple 
cpus, but I find only a passing mention of Photoshop, and that mention said "multiple". 
Using Activity Monitor, I see that Photoshop CS2 does use both of my cpus when doing 
Unsharp Mask, Gaussian Blur and Bicubic resizing. (Lightroom also uses both my cpus.) 
Does this mean that Photoshop is written to use only a maximum of two cpus?

Anyone out there can verify how many cpus Photoshop CS3 uses on four and eight core 
machines? If the answer is "two", then I should stay with the setup I have until I am 
compelled to upgrade my hardware by software features. (From the very minimal 
difference between the four and eight core Pro, it doesn't use eight well.) According to the 
charts in the articles I mention above, CS3 runs slower on a G5 than on a Pro, in fact 
slower than CS2 on a G5 - so I don't want to upgrade Photoshop and stay on my G5.  I do 
not find the new features of CS3 worth the major upgrade in hardware. Ditto Lightroom 
1.1.

If the answer is that Photoshop CS3 uses more than two cpus, then I don't know how to 
understand the MacWorld reviews.

I found the articles at macworld.com:
www.macworld.com/2006/08/firstlooks/macprobench/index.php
www.macworld.com/2006/08/reviews/macprorev/index.php
www.macworld.com/2007/06/firstlooks/ochotests/index.php
www.macworld.com/2007/07/reviews/macpro8/index.php

Michael