Snowsurfer

Hi There,
I am looking to get into some riding again, and was wondering if there is anything decent in full/dual-suspension that would fit a $300-$400 budget.

I was looking at Diamondback, and Ironhorse, which seem to be a step-up from the department store brands from places like Walmart, but not a big step.

Would that be decent? I mean aside from the parts, like the fork, rim, rear suspension, and brakes, can't the frame at least handle similar punishment like the Trek Fuel's or Norco's, or Specialized's?