im in the telecom industry and VoIP is becoming huge and most studies say the majority of calls in the future will be over the internet. but the domain itself is not worth much maybe $xx- low$xxx to an end user. dsl is just the medium to get you there like cable, dedicated T1s, Fractional T1s, WiFi, and plain old dial-up. now dslcall.com or dslcalls.com makes a little more sense. for more info on the technology do a google search for 'VoIP' or 'Voice Over Internet'
good luck