An all Parasound system - Good idea?

My brother- in- law visited last weekend and heard my 2 channel system for the first time.  Slightly ocd, he spent much time online and emailed me last night to say he was going to put his own system together and was planning to buy all of his components from Parasound, in part because he thinks a single brand will optimze performance and compatability, and because he is enamored by the John Curl connection. To that end, he plans to buy  a JC2 Preamp, A21 Amp and JC3+ phono amp.

I have told him focus on  speakers first, then source components. That notwithstanding, is the "All Parasound " a good idea to avoid the possibility of components not playing nice together or should he not focus on brand loyalty and shop for "best in class" components instead?