You're wise to get multiple estimates, as I think those companies charge a pretty penny. I don't know if the remediation companies include the restoration work, but if so, you may be able to get a better deal on that if you hire the finish trades yourself (drywall repair, painting flooring, etc.).

Does your lower level have its own HVAC system, or is it shared with the other floors? And do you have interior-insulated ductwork? If so, it's almost impossible to clean. I work in commercial construcrion industry and I have seen some NASTY interior-insulated ductwork covered in mold.

My main concern would be where is the moisture getting in? Is there one failure point, or is it just weeping through all of the foundation walls? Do you have an exterior waterproofing membrane, and an interior perimeter drain system that daylights to the outside or is pumped?

Good luck with the cleanup. I know that is no fun at all. Hopefully USAA will take good care of you.