Let us know what you think. Changing processors can be expensive. If you are buying from Craig Shumer from Theatermax, he does not offer returns, so you'd have to try to sell it on your own if it doesn't work out. But, he does offer his own full warranty on any upgraded Theta you buy from him.
I went through three different processors when I was looking to upgrade from my old Krell HTS 7.1, before just deciding to go back to Krell with a S1200. It definitely was an expensive journey.
"One of five best processors in the world" is really based on the eye of the beholder. Some people will put Datasat and Trinnov into that area. It all depends on what you think makes up the best. Datasat and Trinnov have very specific processing features, but I do not think either of them have the best analog stages. Same for Meridian. Bryston has good analog stages, but poor DAC/digital card and their analog stage is voice to be soft/laid back. Bryston's new "SP4" offering might be better on the DAC/DSP side, since they are adopting the base Storm Audio product as their base platform and plan on implementing their own discrete Class A analog output stages.