I have used Niagra cycles. They are SLOW, and that is compared to a sloth.
Jensonusa.com, pricepoint.com are my most used. I used to use another back in the day that closed/merged with performance bike, then performance prices went up and I will no longer do business with them.
Jensonusa.com is, for me, has the best prices and quickest service, and any order over $50 (some large items excluded) ship free!