That’s how I do it too, it’s just the most reliable way to do it because it’s the real IE6 youre using, not something else. Just…if you’re going to develope for crap develop for the right / real crap…
You can use ies4osx (http://www.kronenberg.org/ies4osx/) to do this, which runs the applications ‘natively’ through a Darwine (what is best described as a Windows emulator for the Mac). I say ‘natively’, as the applications run in horrible X11. But the page displays just as it would on a PC, which is good enough for me considering how little often you have to launch it.
Browsershots.org does a fairly decent job of showing you the whole page, but the load time can be a bit ridiculous. Still, it’s handy for seeing a good number of older and lesser-known browsers.
Another trick with http://www.browsershots.org is to only choose the browsers you wish to test, not the default settings. It will decrease the load time quite a bit.