Purchased a 2.0ghz about 6-weeks ago, upgraded the HD and RAM and couldn't be happier. Yes, I could afford the 2.26, but it was hard to justify the price difference (since that was the total cost of the upgraded HD and RAM).
My Mini runs everything from Slingbox to iMovie to CS3 to iTunes without a hiccup - all while powering two monitors.
I have a MBP 2.53ghz and honestly not a huge difference in speed between it and my Mini.
$150 is a $150, my vote would be to save it or even better take your wife/girlfriend out for a nice dinner and a movie. You will have a VERY happy mate, plus a new Mini to boot.