Here's some more food for thought. Did Comcast give you a DOCSIS 3.0 modem? 30Mbps/6Mbps has almost an indefinite requirement for a DOCSIS 3.0 modem especially due to the upstream and downstream requirements. 30Mbps is near the limit of most QAM265 systems per downstream channel. If they gave you a D2 modem, get it swapped for a D3. That should fix the slow speed issues you're seeing. At the lower packages, a DOCSIS 2.0 modem does work fine.
EDIT: Re-read the orignal post. That's a DOCSIS 2.0 modem. Also, from my own experience with the RCA/Thompson DCM425 units, those things are awful. It may just be the way Time Warner configures them or their firmware though! With my own experience, the RCA modem you have chokes at around 10Mbps, and often locks transfers at an unstable 8-12Mbps, and while it can do PowerBoost up to 30Mbps on 10-15Mbps profiles, it really struggles in real life transfers. I'm not quite sure how it performs in bridge mode though!
dwt66 got a reaction from mudmanc4 in Closest back to back / Most consistent speed