Thanks for asking this. I am going on, hopefully, my first Regent cruise next year (RSS Splendor, European Transatlantic - Rome to Miami) and I bought all my clothes from JC Penny and Target! The JCP ones look much nicer and country-clubish.
After seeing pictures of people's closets from their suites, it was clear that I will have no problem fitting in on Regent.
Now Cunard, might be another story. I would like to sail/cross the Atlantic or Pacific on a real ocean liner one day, and Cunard is the only one building them.