Just don't get a CX serie PSU ,,, for example the 600w cx is rated 480w, so it's not even a good 500w
What are you talking about? Maybe the older design was like that but the current V2 model is certainly rated correctly and tested by JonnyGuru to perform well under load even when above it's 30C rating.
Edit: ok, I see what you mean now. The 12V lines are rated for 480W only. But this is actually better than most other low-power units out there. Typically only high end PSUs provide the full rated load on 12V lines alone.
A lot of average quality 350-500 W units won't even handle 50% load 24/7 for long.