2 PSU link

Background: Need to link 2 PSU so when I start the mobo they both start at the same time. right now i have been using Add2PSU solution, quite simple and very happy with it, but it cost $12.95 each + shipping, for the cost of powering this once in a blue moon, I think is not worth it.

Question: can i get away from it? how? could i just power the mobo PSU first and then the other PSU powering the 3 other cards after? without the physical link?

thanks in advanced