I have no experience with them and I haven't even heard much about them but another option would be Model Sounds from Canada. Their soundclip page shows they have an Abrams sound set, but I don't see that you can actually listen to it.

This looks to be another stand-alone sound board that would work if you were using a hobby radio.

[link=http://www.modelsolutions.ca/soundclips_tanks.htm]Model Sounds of Canada[/link] (also known as Model Solutions)