i have tested two ampli with my Raspberry B+.
Hifiberry = Perfect. 2x 25W
Price= 49,95$ without shipping
Sound : Good
Supstronics X400 = good. 2x20W
Problem with the box and the height capacitors. Benefice: IR receiver, volume adjust in the board,
Price=34,11$ with shipping
I have 2 Suptronics X400 and 8 Hifiberry with enclosures DIN