As I mentioned in my previous post about my attempts to get IPv6 tunneling going through my AT&T DSL connection, I had been on the phone with level 2 support at AT&T.
The support guy mentioned trying a 2-Wire 2701 DSL modem, since that modem allows much better control over the various options. Originally, I was skeptical, since the 2-Wire has an internal wired and wireless router, which is functionality I don't want nor need, since I have all that installed already with other devices.
In particular, I was concerned that the router would only give out private IP addresses to the machines behind it, and not, like the Speedstream 4100 and the Motorola 2210 did, assign the public IP address to one of the machines.
Once I learned that the 2-Wire allows assigning the public IP address to one of the computers behind the router, I decided to go ahead and get one on eBay. Now that I've had it for over a week, I am pretty satisfied. It indeed does what I want it to do, and seems to be one of the least crippled DSL modems out there.