There is a lot of room under the street side bed, and the deck has lift supports so ours actually pops up almost too easily. Our 2551 has the sub-woofer there, not sure if PC still does it like that, seems a waste of space and I may remove it.
The space under the bed I noticed to stay cooler than anywhere else in the coach, so I lined the larger portion behind the wheel well with 2 layers of 1" foil faced styro insulation with a lid to match. It is kept cool by alternating frozen milk bottles to the freezer, once a day before bed. We use it for extra drinks, veggies and fruit, wine and mixers. We eat a lot of greens and there is never enough fridge space to store much bulky items. Works great, stayed 50 even when it hit 100+ outside, off-grid no AC. Even without the cooler things stay tempered under there.
It could hold several unruly grand kids, too, when they need to "chill." Without the cooler built in, that is.