I think you could expand the 3rd guideline (the purpose) into 3 main parts like Primary Purpose, Secondary Purpose and Tertiary Purpose for example

for the hard-core power-user:
PRIMARY: Gaming, graphic design, Chatting, movie editing
SECONDARY: Music, Movies, internet capabilities including online gaming
TERTIARY: Document typing, slideshow, blogging

so this way 1 could recommend better GPU's instead of guessing if the person really puts gaming 1st or 2nd so they won't waste time recommending some entry-level GPUs.

another example:

for the office clerk:
PRIMARY: office typing
SECONDARY: movies, music, internet
TERTIARY: gaming, online videos

so this way 1 would just recommend a mid-range GPU and a mid-range processor with only 1GB RAM needed so as not to waste money on unnecessary power.