That sure sounds like a wonderful system to me. For sure it screams past anything I use and no doubt it will serve you well for many years. With all the bays and expanability you have, it may be years before you feel the "lust" again.
Since it is only the towers that have the G5, everything else being G3 or G4, your DP will be supported for a long time. Not to worry, just enjoy!
Harv