System bottleneck?

Hi all. My system is made up the following:

Biamp with Parasound a21+ (LF) and Rogue ST 100 dark (HF)

Don Sachs 2 preamp, Marantz SACD 30n, Rega p3 tt,

Legacy Signature SE speakers, pretty good cabling throughout 

It all sounds very good together but if you were looking 

to upgrade where would you start? Just curious what others 

would see as weaker links in this system.