IMO actinics are not "necessary" when running 10,000 MHs and up. Running 10,000k bulbs you may WANT actinics for the color but that's about it.
I'm running my 110g with 2-400w XM 20,000k MHs with out actinic lighting. I do have two 110w actinics I use for dusk/dawn but they do not run through the day.
I agree with the fans... I do not have a chiller... but do have fans in the canopy and run a fan over the sump during the summer. Also, 250w MH are not going to produce that much more heat than 150w MH.
btw, that's a sweet setup promisetbg!!!!