With Guitarsuite there isn't any cab emulation choice, so you'll have to run whatever preamp through their modelling of an entire amp chain... so in the case of the JCM900, the JCM900 head emulation plus their emulation of (I'm presuming) a 1960A.
Guitar Rig gives you a wide range of cabinet choices, but from my experience it's all quite poor. In order to get a workable tone, you need to mix and match a variety of cabs to get a full sound, because they individually just don't give the same impact that a real cab does.
There's also impulse modelling... although I've never had much success with it.