If you're looking for powered, augmented battle-armor, akin to Starship Troopers, and not just armor-plated suits, try these links:

REMC's Third Eye Function
3D Comic Collective
Cyo-Bit L@bo

remc has plenty of sci-fi characters, and some of them wear trooper armor. Check his "Coming Soon" page for a glimpse of more.

The Warhammer stuff at the 3D-CC is a bit cartoonish, but you'll find plenty of styles. And you can download the armor components separately (Props Packs 1-8), if you don't want the entire characters.

Cyo-Bit L@bo has a character in powered armor called SAF Protect-gear.