said by ericn32:actually I would not recommend getting a DOCSIS 2.0 modem simply because they will probably EOL'd by the end of 2013 or 2014 the way things are going. TWC in Dallas already has bonding on the upstreams we are the third or fourth cluster to get upstream bonding behind NY, and Hawaii.
By the way, there's a new discussion about the Modem Fee going up to $3.95 per month. I've been eyeing the SB6141, and expect a 25-month ROI.
About the increased speed - here's how it works (correct me if I'm wrong).
Each cable channel gives you about 38 Mbps, and when you're tuned to one channel that's almost fully used, and another has open capacity, the modem has to tune to the other channel to use the available bandwidth. With DOCSIS 3.0, you can tune to 8 channels at once and get bandwidth from all of them, up to your 10 Mbps cap. I imagine that this would deliver more consistent bandwidth.
Also, you might not need the SB6141. It bonds up to 8 channels, giving you about 300 Mbps throughput. The SB6121 bonds 4, giving you about 150 throughput. If you don't think you'll ever want more than 150 Mbps during the life of the router, you just need the SB6121, which retails for $80 on Amazon.
You could also get a DOCSIS 2.0 modem, which are cheaper and most similar to the DCM425 and won't perform any better/worse, just make sure to get one that's DOCSIS 2.0+IPv6 certified. Now would be a bad time to invest in IPv4 equipment.