My gut feeling:
The 300cx is based on the 200 which was not in the same class as the original 300 and 600.
With the cx you cannot use an aftermarket powercord, which can make a huge improvement. If it were me, I would buy the 600 and an aftermarket powercord. (My preference is the Pure Note Sigma.) You will probably get a better sounding amp, plus a lot more power.
The only downside is the weight of the FPB600.
Richard
The 300cx is based on the 200 which was not in the same class as the original 300 and 600.
With the cx you cannot use an aftermarket powercord, which can make a huge improvement. If it were me, I would buy the 600 and an aftermarket powercord. (My preference is the Pure Note Sigma.) You will probably get a better sounding amp, plus a lot more power.
The only downside is the weight of the FPB600.
Richard