I believe that the "best" serial number is 5!
This is not beause I have that particular # but because the amp is a special edition for Head-fi's fifth birthday and is called Headfive, so 5 rules!!!!
It's just like having GRADO HF-1 serial number 1!(Jude, how about a trade?


)!!
That said, I really like having #5 for me



Manuel