Crysis and my Radeon HD4670 Thread

Hi guys, I have been working on a script for a short animated feature, and more importantly pondering over using crysis to run the short in real time. I have a Sapphire Radeon HD 4670 512mb ddr3 card running on q8200/4gb ram/vista 64.

Now I am not sure if this is the right forum, but I cannot run crysis in full hd. @ 1440x900 I can run everything high quality. Now I was using sandbox and I loaded up a level just to check it out and once it was running I was viewing it with lots of AA lines and so on. 

My question is, if I were to use sandbox to create some camera move, then render it out as an image sequence at full 1080p hd, will the fact that my graphics card cant run 30 fps 1080p make a difference ? For example in maya, there are times when the machine cant show you 30 fps but when you render it out, you do indeed get all the frames with no drop. I have some money now so I was thinking I should get another graphics card, IF it will affect my rendering process. I am not trying to improve my gaming experience really, I got the 4670 because it has multiple outputs and it helps with my setup for 3d work. 

So any suggestions on what I could get under $200 possibly ? My motherboard can do crossfire also if that makes any difference. I got my current 4670 with the intentions of crossfire at some point, but I am unsure about the real benefits for creating a machinima on crossfire you know. 

I thank you very much for taking the time to read this. Hopefully I get some answers now

The question is: where and how does Crysis dump your image files?
I know from Unreal that it can dump single bmps, which can later be compiled into lossless video. So, in that case it doesn't matter what fps you get in realtime, since the movie will be compiled from 30frames (per second) later, anyway.

Unless you want to make a realtime machinima you have to get beastly hardware, but in case there is an image file dump, you have other options; and I guess there is...