What do you feel the shortcomings of the sounds you currently achieve are ?
I personally would not spend $200 on a guitar sim vst if you already have the podfarm basic version, amplitube and guitar rig. Im not trying to be a dick but whatever your trying to accomplish soundwise you should be able to achieve with those options, if thats proving difficult its time to rethink your method because the technology is probably not whats holding you back.
It could be a tactile thing, like your missing the response of a real amp setup, some people just dial in tones better with knobs and speakers, if thats the case then you should try out a real amp or something like the Laney ironheart studio for more of a hybrid approach.
If your just trying to blow money on a fun new thing Ill add a vote for x50 v2, its badass at what it does.