It's possible that your phone is to blame for the hangup on phone ring. DSL operates using sub-audible signals over your phone line. If your phone is old or poorly made, it may emit signals in the general range of the DSL modem. Putting DSL filters between your phone and the line may help prevent this interference.
Regarding DSL modems, I've found the 2Wire brand devices work exceptionally well. But they only work for AT&T connections. My dad worked for AT&T (well, first it was Pacific Bell, then Southwestern Bell...) for many years, and for the last several years he was the DSL installer for our area. We always had the 2Wire devices (which are usually the more expensive options you purchase from AT&T. Around $100 for the device. It replaces most routers as well though because the 2Wire, in addition to being a DSL modem is also a 4- or 5-port network switch and a wireless router.
You don't usually interact with the control gui of the modem. An HTTP gui just means that in the case you need to set up your wireless or manage a more complex firewall option, you'd log into a page hosted on the modem itself to make these changes. They're generally as easy to use as an online banking page, in my experience.
ADSL2 is a collection of technology standards that allow higher throughput speeds on DSL. DSL is really the slow child of high-speed internet. Some of this is due to the fact that it usually has to run over old copper lines which were meant for analog telephone signals, not digital data signals. ADSL2 is supposed to help bring it into a more competitive system by at least addressing the protocol standards and such.
If you're on an old copper connection, you may want to look into an ADSL2 modem. But if it costs a lot more, I would not consider it enough of a requirement to pay a premium for it. More of an "it's nice if the device has it, but not a problem if it doesn't" sort of factor.
