Best use adding SSD to speed up Photoshop?

Question

This is actually a multiple question post.
My aim is to try and cut down some time on Photoshop, mainly when using big files (over 2 or 3Gb) not only when reading and saving but most importantly applying adjustments or modifying image.
Almost every other day my daily working files go to 2 or 3Gb each and its painfully slowing me down the time it takes to sometimes apply some transformations let alone the process of saving as safeguard with regularly over the day.
Today was working on a 10Gb file and it would take Photoshop close to 15min just to open the file...flattening the image would take around that too and saving a little over 25min.
I know on Mac's its a pain in the back to move the system swap files to another disk (although theres an app that supposedly does that for you (Xupport).
I just find it hard to find out what best use I could make for a SSD I would add to my existing configuration that could speed up Photoshop on Mac:
1. Install system and apps?
2. Use system swap and leave system+apps in other HDD?
3. Use for Photoshop scratch disk?
4. Any of the above in same SSD? 
Other pertinent data:
Every project once completed is moved to a backup USB disk so the durability/reliability of SSD isnt really a problem althought I aware SSD has some issues regarding tearing over multiple re-writting over time.
Mac Pro dual quad-core 2.8 (MacOSX 16.2 + Photoshop CS4)
8Gb DDR2 Ram (soon to be 12Gb)
1 SATA  320Gb for data in use + system +apps
1 SATA 500gb for  general purpose data and backups before going to external HDD plus Photoshop scratch disk
Ty in advance for any help.

Answer 1

You have plenty of system to throw at Photoshop. The application ought not to slow down to the point of un-usability but I'm certainly not working with images at that size.
Here are the techniques I have used to make almost all applications faster:
Add more RAM. That way, any application you use won't have to be swapped out to disk if you are running lots of applications.
Move OS X's swap drive to something faster.
In the case of Photoshop, move Photoshop's swap drive to something faster with lots of space
Get a hotter graphics card that your applications will take advantage of.
With respect to #1, Adobe's Photoshop is a 32-bit application. Photoshop will benefit from your Mac not using its swapfile as additional RAM but Photoshop will not see any more than 4GB of RAM and will probably see a lot less than that (most 32-bit applications use something like 2GB).
With respect to #2, here's how to do this:
Edit the file com.apple.dynamic_pager.plist, located in /System/Library/LaunchDaemons. Replace the/var/vm path with the full path to your swap partition. In my case, the entire plist ends up looking like this:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
                <key>Label</key>
                <string>com.apple.dynamic_pager</string>
                <key>ProgramArguments</key>
                <array>
                     <string>/sbin/dynamic_pager</string>
                     <string>-F</string>
                     <string>/Volumes/Swap/.vm/swapfile</string>
                </array>
                <key>OnDemand</key>
                <false/>
</dict>
</plist>
Save and reboot, then check your new swap location is being used with this command:
ps -wax | grep dynamic_pager -m1
Finally, you probably want to clear out any old swapfiles from /var/vm:
sudo rm -rf /var/vm/swapfile*
If you have two SSDs, use one for OS X, the other for Photoshop. And remember, for an 8 GB file, Photoshop will want a lot more than 8GB as its pagefile.
You will want to experiment to see what methods work best for you.
Good luck.