I have the omegastar in my HT, and the FetValve in my 2 channel setup.  IMO, the FetValve is just a better sounding amp, more impact, more dynamics, better transparency, and smoother.  Not that the Omegastar is a bad amp, far from it.  My omegastar started out as an Omega III (the prior model), and the Omega III was so good I sold my Odyssey Stratos amps after hearing it.  The Omegastar is certainly a big step up over the Omega III in detail, impact, and speed.  But the FetValve is truly something special, able to match amps that cost more than it's 2 grand price.