Migrating to new MP, adding SSD

Here's what I would do.

1) Add the drives to MP.
2) Boot from the CD and install OS X to the SSD. I'm pretty sure it'll do the formatting for you here on that drive. If not, you can use Disk Utility from the CD and format yourself if there are issues.
3) Change home directory to HDD of your choice (search for guide on here, it's pretty easy).
4) Copy User folder from your G5 to your Home drive.

It's been a little while since I've done it, but it's pretty straightforward. I'm not sure it's recommended to copy a boot drive from a PowerPC (or any different model machine, for that matter) to your new MP. Someone else will confirm that for you.

Nice setup. Enjoy

for compatibility sake, I'd forgo doing any form of migration from a PowerPC system.
Start new, install OSX on your SSD and place the files you need over. I'm sure OSX is smart enough to transfer/migrate files from PowerPC to Intel just fine, but for the sake of starting with anew install it may beneficial to start everything off with a new install including apps and just manually transfer your other documents and files over

I have the same setup. Just not coming from the G5 (which is arbitrary as you will only be moving the Home folder)
Install the OS and all your "updated" apps to your SSD.
Create the account with the same name (and short name) as your previous system.
Copy your Home folder to the HD of your choosing. It may be a good idea to prune the ~/Library/Application Support and ~/Library/Preferences directories and purge anything you are not installing on the new system. That is my choice as it will keep things even leaner.

Then open System Preferences and choose account tab.
Unlock the lock if it is not already. Cntrl-Click on your account name and choose the "Advanced Options".

In Home Directory box choose the location of your newly moved Home folder.
Don't change anything else!

Click OK and apply if needed.
Reboot Mac.

Verify that your new folder has the House icon and you can get to it in something like Finder.

Go into HD/Users/ and delete the remaining Home directory folder.

That's all. You'll need to do 2 backups now if you were using SuperDuper. 1 for the boot and 1 for the data portions unless someone else has a trick to have it seen as one contiguous volume and on 1 image file.