No, more tubes do not necessarily mean better sound. The Fusion preamp appears to be an upgraded version of the preamp/DAC, though. So in this case it is likely that the 4 tube version sounds better than the 2 tube version.
I have read good things about the Fusion on this site. The DAC is not a gimmick as preamp/DAC combos are becoming more common. The way DACS are improving, though, you may want to have a separate DAC so that you can upgrade it separately from your preamp. Although you could also upgrade your preamp/DAC to a better preamp/DAC.
From the Jolida site I'd say the preamp/DAC is their good/value model while the preamp is their audiophile model. I agree with mesch that you should give them a call and talk over with them which might work best for you.
If you do a search there are a number of threads here about the Fusion.
I have read good things about the Fusion on this site. The DAC is not a gimmick as preamp/DAC combos are becoming more common. The way DACS are improving, though, you may want to have a separate DAC so that you can upgrade it separately from your preamp. Although you could also upgrade your preamp/DAC to a better preamp/DAC.
From the Jolida site I'd say the preamp/DAC is their good/value model while the preamp is their audiophile model. I agree with mesch that you should give them a call and talk over with them which might work best for you.
If you do a search there are a number of threads here about the Fusion.