All you need to work with sonar is a sound card better still a sound card with an S/P DIF input that you can use to get guitar / vocals / bass in with.

The killer with Sonar is the cost of the plugins:

Autotune 4

300 bucks

Waves native gold

1000 bucks

Sonar 4 producers pack

700 bucks

ouch !!

With that lot their is not much you cant do !