About a month ago, I did exactly the same thing - changed from PC to Power Mac G5, mostly for photo editing and music. The new Intel Power Macs (or whatever they are going to be called) won't be as fast as the current G5's at things like Photoshop because the new Macs will be Intel and Photoshop is PPC - it will have to be emulated under Rosetta. For the fastest Photoshop engine around, likely for the next calendar year, get a Power Mac G5.
I bought the exact same machine you are looking at - dual core 2.3 GHz with lots of memory. I *love* it. It is a great machine.
After lots of looking around, I bought on line from
www.macconnection.com. They offer better prices (in this case, a $150.00 rebate on the Mac itself), plus an awesome selection of other stuff. I also picked up a Viewsonic monitor there for about $100.00 less than anywhere else, AND Microsoft Office for Mac (also PPC by the way - doesn't run very quickly on Intel Macs) for about $20.00 less than anywhere else.
Finally, and this is the killer, in many states you won't haver to pay tax. The Apple Store, much as I love it, is obliged to charge you tax.
So, buy on line and save dollars!