What's the best way to go about saving card images in Illustrator (CS3)?  
 
I'm assuming it's:
1. create a 5"x7" document & work on it
2. File > Export as High (300 dpi) JPG
 
But then if I choose high, very high, or maximum quality, the images are over 4mb and my (new) computer slows to a crawl.  
 
Would low or medium quality still look ok?  Or is there a better way to save JPGs from Adobe Illustrator?