Onkyo and Yamaha stuff are pretty much equivalent. I've owned a lot of both.
They do both make some pretty good stuff in their audiophile lines (like
high end audiophile Yamaha amp and SACD player). The Onkyo
A-9555 integrated amp is winning the hearts of a lot of audiophiles on a budget. So both companies are good at offering good sounding components.
but your components are pretty much the normal consumer grade stuff, I would be surprised if one sounded a lot better than the other. In this range, I'd definitely be more inclined to look for a budget amp like a NAD or Cambridge Audio for two channel duty. I would not want to use a 200Hz crossover for my speakers, most of the time, you want to cross over lower than 100Hz to prevent localization of the sub (you would be able to tell where the bass is coming from)