what do I upgrade?

Current system
wadia 302
marantz vc 5400
krell showcase pre/pro
krell kav 3250
adcom 5400
wilson sophia
wilson cub II(as center)
snell sr30 surround speakers
all nordost red dawn cables

System originally started as HT but I want to improve on the 2 channel side. What would be optimal path in upgrade? Should I start in pre amp or upgrade amp? What models should I be looking into?

Thank you in advance for your advice.