I'll mention Station Playlist again. We migrated off SAM several years back, and for Internet providers (also for terrestrial stations), this is a wonderful program, but a bit of a learning curve if migrating off SAM Broadcaster. Still, the variables are tremendous if going with the Pro version of Creator and Studio, and well worth the expense in the long run.
If you want a great program, but needing a superior sound-card to run appropriately, and also uses the Linux OS, look at Rivendell. You'll spend the money on a sound-card over the cost of the software, because Rivendell is Open Source and free, but the sound-card to optimally run the program will cost you roughly the same or more as the cost of the Station Playlist Pro software.
If you are a Linux newbie, you can download RRAbuntu to get you up and running on Rivendell. Even if you don't go with Rivendell, it is still a fun program to play with to see what it will do.
SPL is a great Windows program, and one I would highly recommend. When funds come in for our station, we are planning to invest in an AudioScience card and use Rivendell for the superior features. In the meantime, I'll say that Station Playlist is our Windows program of choice for play-out software.
On another note, if your station isn't that complicated, SAM or Station Playlist will fill the bill nicely.