I found a non DVR version on ebay for 60 bucks. There are a bunch out there, just search for Motorola DCX3200. Check with TWC to see if you can use this on their system.
If you want a DVR, I'd probably go TiVO. Cable DVRs royally (and universally) suck. All new tivo units use a cable card. Even if you bring your own DVR(EXCLUDING TIVO), i believe TWC can still charge you for the DVR service (not 100% on that one, you'll have to ask)
Tivo.com
Edit: When you talk to them, there's a 50\50 chance the operator will tell you you are not allowed to use your own equipment, or they don't supply cable cards. This is a complete lie. Under the FCC's FCC Rule 76.1205(c), a consumer is allowed a cable card device minus the set top box fees. Under a different, but similar act, it requires cable companies to allow the consumer to bring thier own equipment, though i wasn't able to find the exact rule.