The limitation isn't usually your Internet connection or the equipment you have to reproduce the signal once you receive it, it's the resolution of the digital stream that's being sent, and that's not something you can do anything about.
Most Internet radio stations provide a 128 kbps signal, at best, which is about the same as the lowest quality mp3 file you're likely to encounter. A good DAC and other downstream equipment will make the best of that signal but that's more a matter of doing no harm than improving the low resolution source.
But, even with that limitation, Internet radio is a terrific way to discover new music, along with Pandora, Mog, Spotify and other online resources.