The software can do it - can your hardware?? Catalyst software can output pretty much any resolution up to the quicktime limitation - the question should be 'can my hardware run this content?' And thats something only you can answer by testing.

I don't think that anyone on this forum can categorically say what your system is capable of. You need to test these scenarios on your machine with your content. As Richard said, there are too many variables in hardware, OS, software etc.

Personally, I would let an old G5 system deal with SD and lower and would only use a MacPRO with high spec graphics card and SSD drive for anything more than that.

Let us all know how you get on.

Nev.