Computers Video Card Power Houses

It's been a long time since I've been able to check out the latest in Video Cards and give good, informed advice about what to purchase. I had a few questions that I hope someone here might be able to answer-

512 Mb - Have we finally crossed that threshold in terms of Vid card mem? If we have are the cards worth buying? Do they run hot enough to rotisserie chicken or have heat sinks improved?

ATI or nVidia - I'm currently running a GeForce 6800GT (256Mb), what's come out since then. What about ATI? I've never really followed thier card line- what's out that's hot? Unreal 3 is coming out, what do you guys recommend to run that baby?

Video Editing - I want to get into creating my own AMVs, I've got enough system memory to last me a lifetime, but is my Vid card powerful enough to handle an app like Premiere for the amount of Data I want to edit? I plan on ripping, converting and editing DVD vobs (legally, ) to build the AMVs. I don't plan on creating and rendering my own CGI's, just video editing.

Hopefully someone will be able to help. When it comes to my computer money is an object, so the latest and greatest is always welcome, but if my current hardware will run the games w/o any problems there's no reason to upgrade. What do you guys think?

~The Indefatigable Wert