I bought a refurbished model from Microcenter over 2 years ago (for $24.99) and that was version 2, so I'd be surprised if any of these were version 1. It looks like vesion 2 and above can use DD-WRT, although I haven't tried it:
http://www.howtogeek.com/56612/turn-your-home-router-into-a-super-powered-router-with-dd-wrt/
I originally was planning on flashing mine, but the stock firmware really did everything I needed, so never got around to it. Mine is working with about 15 devices at the house, and I also have an Ooma VOIP going through it (wired), and everything works well, so I don't want fix something that isn't broken. Apparently you have to use a "mini" version of DD-WRT, at least with V2.
My Roku will often choke trying to play long, higher-res, home server movies through the n-wireless and a Plex server, but I don't think it's a problem from the router itself.
Edit: I just checked, and I have 20 devices connected to it at once - not bad for a cheap router...