[Thoreau Bakker] "I've heard something about hardware acceleration, then I've read Vegas doesn't support it?"
That's correct. Don't waste your money on a video card. Vegas won't use it. The one you have is fine for Vegas editing.
You didn't say what version of Vegas you are using. Vegas Pro 10 has added better support for Canon files. If you are not using VP10 you should download the trial and see if it solves your problem.
If you are using VP10, then what you want to do is buy CineForm NeoScene ($99 USD) and convert your Canon footage to the CineForm codec. This will edit smoothly in Vegas.
~jr
http://www.johnrofrano.com
http://www.vasst.com 
