I do not and will not dive a scubapro mk25 first stage but wont dive anything else besides a scubapro mk17, MK2 (deco gas only), or dive rite first stage although the apeks DS4 would be fine on a deco gas for me too. I own like 8 regs all are mk17 first stage accept 1 mk2 on my deco bottle.
as far as second stages are concerned I love the S600's and only own them accept 1 dive rite (deco reg) and one R190 for backup. The S600 works for me in the 36 degree water and the adjustment is necessary for my diving habits.
I hate octo's, I wouldn't ever drag one with me ever again....ever. yo dont need one and neither does your buddy. if you think your ever gonna need an octo spend a bit extra and make it into a 19-40 cubic foot pony setup. the reasons for this are all over scubaboard and their are proponents on both sides of the fence. I feel that octos are a total complete waste of money and dont dive them but I carry a redundant air source like a 19 or 40 or use doubles with dual outlet manifold and 7ft hose.
enough said.