That's a good upgrade path. I too found Volumio unreliable and switched over the Squeezelite which was very stable. Lately I've been using Roon which is also stable albeit at a cost.
On a budget for your 5v supply I would buy a 6v toroid and a regulator board from diyinhk:
This is max 1.5A but that should be ok if you're not powering stuff from the Pi's USB ports. A technically superior option can be found here: