Ask HN: Best way to make a hardened Tor exit node?

I find myself lucky enough to have an abundance of bandwidth available at my home. Rather than let that potential go to waste, I would like to set up a Tor exit node. I have already contacted my ISP and they are fine with me running it as long as I'm willing to deal with the hate mail.

My question is, what would be the best platform for running a hardened exit node? Here's my thought process: an exit node would paint a pretty big target on my systems and I want to ensure the security of anyone wanting to utilize that exit. I want this segregated from my home network, and have found out that I can set up a switch to get a separate IP address from my ISP.

I was thinking ideally this would be run from a dedicated device (was hoping for something like a Novena but I currently lack the funds). Since I'm going for a hardened system, my first instinct is to go for OpenBSD as the base system.

If you were looking to do something like this, what hardware would you use? Would you go with OpenBSD or a different OS?