PCM XR 450HP Versus XR 550HP

I thought I would enter a new thread today to see if I can get more details on HP needed for the Natique G23. The XS 550HP is very costly and I was avoiding it hoping the 450HP would suffice. Now I am waiting on a quote for the all new XR 550HP which is less than the XS 550. I understand the main difference is that the XR is similair to the XR 450 and does not have staineless pipes like the XS. Two questons...Will this new XR550 be reliable? Is 450HP enough for this boat that seems really large? We usually have 10-12 people on board at any given time.