Im considering upgrading my amp,wich is a nad c320 (50wx2) , im using b&w 683's,so I think they underpowerd . More powerful nad amps are quite expensive,a 80w x2 would cost upward of R7000, a 150w x2 nad amp would be upward of R13000. Im only looking at nad 2 channel amps. So how much would be considerd too much for a decent equivalant 2 channel amp? I want to consider all options.