I have now worked out what my next animation is going to be .... No real story again unfortuntly;-)  but it is going to be a giant zigarat/pyramid surrounded by forest and rocks . There is going to be some kind of fighting going on at the top of pyramid with poser figures. As I mentioned before I rendered this at 1200 x 900 for my next animation I have been advised to go much lower and in some cases higher. 
If I rendered this next animation at 320 x 240 is it going to look real bad?
I want it to look good when viewed on full screen not full of artifacts/blocks/noise.

Any help would be great any suggestions for effects to use in my animation I will be gratefull for also.

My main concern is what to render it at .... 1200 x 900 looks pretty lush but takes a long time to render.