Which leads back to my original question: Should I run two miners on one psu?
yes, technically you can. but as you mentioned, it is definitely safer to buy new PSUs for each miner. just because, half day of non-mining because of faulty PSU will cost much then new PSU.) I will buy something from enermax, at least with gold certification but considering platinum now.)
Get whatever you feel safest with. Don't cut corners. Solid PSU's can be re-sold, or re-used at a later date. Killing your unit by cutting corners will only mean you may loose out in the long run.
Also is you are running one PSU for both, and the PSU fails, that's both units out of action till the situation is resolved.
I wouldn't run the two on one PSU, good call there.