Difference between "at least for one hour" or "for at least one hour"

I've found following sentence in a book.

I usually listen to music for at least one hour.

Please someone tell me whats happen if I change the position of the "for" as follows.

I usually listen to music at least for one hour.

Does both sentences are grammatically accurate and correct?

Furthermore, is there any changes in the meaning of the above sentences?

Thanks