2005 Suburban cargo and under rear seat dimensions?

Hello all, I recently picked up a new to me vehicle. Anyhoo, I'm ready to plan a new build and start ordering amps/subs and box plan. I googled it for a while but couldnt find what i needed. How wide is the rear cargo area panel to panel behind the 2nd row seats, i guestimate 49-50"? Also, what are about the max dimensions for cramming an amp under the rear seat? I have had a major life event recently and i am unable to go measure for myself. I greatly appreciate any help!!