The subsonic-service.exe process uses (in your case) 123 MB of native memory. Of this, 60MB is allocated to the Java heap. This is where all the objects of the application lives. Currently, 23MB of the heap is in use. The remaining 123-60=63MB is being used by the Java virtual machine itself (and for other things like thread stacks).
The subsonic-agent.exe is simply the control panel and tray icon, and doesn't need a lot of memory.
There should really be only one instance of subsonic-agent.exe. Does it occur twice in Start > All Programs > Startup?