I've been using LightSpeed Gaming and I've never had a problem with them in the past couple of years (
http://www.light-speed.com/ ).
They have both TS and Ventrilo servers. I think I pay maybe a little more than...$25 a year for 8 players and they've always been clear sounding and never been down whenever I've tried using them.
Not sure if Ventrilo is better that TS or not...I've never used Ventrilo. =\
A|ice