From my experience with 8500/8550, adding memory does help. Also, using a network connection instead of the USB one also is faster for 'heavy' documents. If however text files take long to print, something else might be the case. How much does a 10 page plain text pdf document require? (when the printer is not in stand-by mode of course)
We have a new phaser 7500DX and very slow printing. it currently has 512mb of memory. Will adding more help and if so how much should we add?. We print lots of jpegs, tiffs, and other graphic files as well as text files.