Iam about to connect Pioneer GM-D1004 - 4 amplifier,which is a very small amplifier and does not have to be wired directly from battery.(15A current) . So was thinking to wire it from fuse box either 48 or 47number,so 15A fuse should be ok.Does anyone have experience with wiring this amp?Or should I just go normal battery way?

Is it 15A continuous current or 15A Fuse rating for the supply? 

Mid it is the former then use 20A fuse with at least 2.5mm Sq cable/12awg.

if it’s not got any significant quiescent current drain I’d go battery or fit an ignition relay. Either way I’d keep as much wiring separate with short earth leads.

Amp automatically detect input and will switch itself on. It has got fuse on the back panel 15A and current consumption is 15A. Should be connected to permanent supply as stated on the manual.