I can understand the appeal of selling on codecanyon for the existing marketplace you get access to there, but I would consider an independent checkout for the website. Your design and branding are well done and signal high quality, while codecanyon has more of a script/component flea market feel. I think taking someone out of the flow of your site to buy there is a bit jarring and might cause people to reconsider, especially enterprise-y customers.

I also have the sense that you could probably raise your price significantly. Considering what businesses pay for a service like basecamp, they aren't going to blink if you charge them, say, $250 instead of $45 if the software is good. For a business of any size, $250 and $45 are essentially the same as a one-time cost--negligible.