This sounds like good advice...
If you increase the ram and increase the amount of RAM that photoshop can use (in the photoshop preferences) you should get good performance.
OP - What are you deeming to be 'heavy' Photoshop use? I work as a web/print designer so cover everything from working with large scale images and artwork files, to complex vector files with tens of thousands of points, processing images and occasional video editing/animation (across all various CC apps).
At present I am working on a 2008 Intel Core Duo 2.53Ghz with 8GB RAM. Whilst it occasionally struggles, like thekev said: "anything would be a major upgrade"
I waited for the Mac Pro announcement and quite frankly, it looks like it would be overkill for anyone other than gamers or those doing lots of video editing.
After seeing the spec of it against the price, I decided to get a iMac 27" with 512GB SSD, 3.5Ghz i7, 32GB RAM (upgrading myself when I receive it) and the 4GB graphics (which again, the standard would be more than enough for photoshop, I just wanted it for video work).
I can see the fascination with the Mac Pro - although some deem it as looking like a trash can, I like it - it's a genius, functional design (in terms of cooling/size etc). However, the price after adding a screen, upgrading the RAM and upgrading the SSD, adding applecare it would be around £3600-3700. The iMac spec'd above that I ordered cost under £2895 inc applecare - that's £700-800 that could be spent on a massive external storage system, some networking gear or graphics tablet.