Tell us about yourself!
Instead of just using 3 single cell LiPo batteries and wiring in the protection circuit, could I just replace both with a 3S pack with protection already built in? i.e. this one: http://www.hobbyking.com/hobbyking/store/__31315__...It's cheaper (for me) than to buy 3 separate 18650s, but I'm skeptical if the 3S pack's output current will be enough for the yamaha amp you linked.
40W Bluetooth Portable Speaker (Improved Version!)
LED Cube 8x8x8