Appropriate to ask for advice on upgrading on this site?
For instance, if a user says "I have this computer was set up a, and $500 to spend, what are the best upgrades to spend my money on?", will this be allowed?
I'm going to go with "no" here -- it's a shopping question as you phrased it. Any recommendations that involve spending money are highly time-limited.
If you remove the dollars and simply ask:
If I was going to upgrade my computer, in what order should I upgrade components to get the most performance for my money?
That would be slightly less contentious question and probably one I wouldn't vote to close as it will stay true much longer than a I-have-dollars-to-spend question.