I'm looking into getting a WA7 sometime in the near future and just had a few questions: 1. Is the tube psu a must or can I just get that later on and be happy for now? 2. Is the onboard DAC good enough or would I want an external one? - I want to use this as a preamp for speakers so an external dac being needed would pretty much make it a pointless upgrade from what I have now as it would take up the RCA in/out 3. Is there a big enough difference from gen1 to gen2 or is it a good idea to save the money? Thanks!