I have always had a problem with Power Armor. I love it. In all its permutations. Space Marines, Terminators, Pig Iron System Troopers, and any of the other 1000 or so variants out there.
But I thinks its really hard to make a suit of PA to suit my Hard Sci Fi bent if need be. You see, the human body, surrounded by metal and composites and servos or hyraulics, motos, accuators, armor power systems, weapons, etc. would just be a big ball when you are done. Thats why (almost) the semi giant walkers in heavy gear may be more plausible (assume miniaturization, power and mobility can be sorted out) that a single guy in Starship Trooper Armor.
Anyway. I found a beautiful illustration on Concept robots that restore my faith in hard sci/non-manga Power Armor. I give you the H.ARM Suit. Beautiful. Illustration and design by Elliot Lilly.