I currently own AE CS4. Now that CS4 is out, I only want to upgrade if there are decent performance upgrades. My thing is this, I work in primarily high resolution 1900x1080 projects, and I want to cut down the ram preview / render times as much as possible.
I'm also interested in purchasing a video card. I currently only have a GTX 275. I've been reading up about nVidia Quadro vs. GTX 285 etc.. Ultimately I wouldn't like to spend more than $1100 together. The upgrade to CS5 costs $299, and the nVidia Quadro 3800 I believe is around $800.
Would it make sense to upgrade to CS5? Or should I just invest in a better video card.
Performance improvements between After Effects CS4 and After Effects CS5 are large. See this page for information about the changes related to RAM and the move to a 64-bit application.
The video card doesn't really matter for After Effects. Spend your money on RAM first. That advice changes if you're using Premire Pro CS5, which does take advantage of CUDA technology and can therefore use some of the features of the fancier graphics cards.
Have a look at this post http://forums.adobe.com/thread/641934?tstart=0 and try rendering the mentioned volumetric project in CS4 (I tried, but stopped rendering after 40min). With CS5 I had over one hour with the default settings and about 3-4 min with the adjusted ones (see my post).
Just test your rendering time for that project