I think you could get well into the "people are paying money for this service" stage of a hosted Django hosting platform without ever having to touch C. Python is fast enough to do most of the systems-level programming you'd need for such a beast, especially since so much of the standard library (socket, struct, asyncore, subprocess) sits directly on top of the fast POSIX syscalls you'd be invoking to do the same work in C anyway.

Going down to the metal may help squeeze the last 10-20% out of your hardware, but the the really interesting and challenging work in coming up with a scalable hosting platform is elsewhere: security, monitoring, process spawning/reaping, deployment, et. al. If working in Python gives you a time-to-market advantage, then go for it. You can hire a C hacker when you have enough business to make the improvement in your hardware utilization efficiency pay off.