I like the size of the logo on your main page, however it can't be used directly as it's a transparent png. Something about that size would work. Between 120px and 140px feels ideal.
Another thing to consider is whether or not you want to encourage people to use your hosted copy or host it themselves. On the one side, it's a cost but on the other, you can update your logo and use logs to see which sites are using it. Unsure about that one.
No rush on this one. Thanks for your quick responses though!