My subs are sitting in the garage waiting to be installed. Its going to be under 40 tonight which means it will be in the 45 degree range in the garage. Any concerns?

Shouldn't be bad for it...I mean, I had the subs in my car in ND at -40* F. At some point, the surrounds just stop moving :)

As long as you let it warm up first before turning it on to make sure any condensation can evaporate, you should be OK....

I doubt seriously that should be a concern since all speakers and components spend lots of time in even colder warehouses and transportation trucks. One thing though it will probably take a little longer to run in (break in).