Does it really, really, matter? I didn't buy a calibration dvd and my 360 games look fantastic on my hdtv. My Wii games look as good as they can in 480p.
You are obsessed with getting things to look perfect, when the differences are barely noticeable.
Just buy like RE4, and find a dark room with a light coming in through the door/window, and use that gradient to get the brightness/contrast good, Or, whenever you go back to the Wii menu, it loads with a full screen of gradient light to dark, it's short but keep loading and changing settings till it looks good.
But damn man, I'm sure your games look just fine the way they are. Buying a "calibration dvd" sounds like a total rip-off. I'm sure getting that grayscale just right really makes a difference.
And it's not even like getting your 360 to the perfect setting will be a one-stop fix for every game. A lot of people had to adjust the brightness in-game for GTAIV, it was insanely dark at night.