I recently upgraded from a PS Audion P10 to P15 and immediately noticed improved bass, better detail and a bit of smoother sound from both of my DACs.
If the P15 is too big a beast for you, I suspect the P12 has the same level of technological improvement compared to the P5 it replaced.
If the P15 is too big a beast for you, I suspect the P12 has the same level of technological improvement compared to the P5 it replaced.