I went from a 7800 card running 4 instances to a 8800 card running 4 instances and just wasn't a stellar difference, so I'm thinking the 8800 -> 9800 wouldn't be a huge diff either.

As far as justifying, as always it's up to you. Personally I pay all of my bills, extra on house, and savings before I have ANY play money. Then with that play money I ask, what gives me the best ROI enjoyment wise? I don't watch T.V., hate going to movies, eating/drinking out just seems horrendously expensive... I like golf but around here that's $40/game (only 4 hours of entertainment)... other thing I enjoy is racing, ROFLMAOExpensive. So for me this is by far the most cost effective entertainment.