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.
I second everything said here. (I definitely did a double take when I saw the CodeCanyon link).
I think the thing to note with regard to price points is that I might be willing to pay $45 "just to try it out", but that definitely wouldn't happen at $250. I'd have to first make a sound decision about the software (through the demo, etc).
I agree that you could probably charge considerably more for this, though I also agree with the poster in another thread about support expectations for a more business-class-priced piece of software.
You could do both: Keep selling the $45 version that maybe includes access to a general support forum, but sell a $299 version with premium support for one year. Then sell renewals for support agreements! It'll be worth it to most businesses to avoid the headaches of having to deal with self-hosted software on their own, and you'll have a good source of recurring income from existing customers.
I also second selling it for $250 and using something other than Codecanyon. I'd recommend using Fastspring (customer, no other affiliation) since it has no monthly fee and takes a lot smaller cut than Codecanyon.
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.