I'm guessing that you should be able to get stock tubes from MHDT. http://dhost.info/mhdtlab/
I run a Squeezebox Duet via coax through the Paradisea+ and I use the fiber connection for the digital out from my Sony NS999ES. I've ripped almost my entire CD collection to PC based storage, so most of the time I'm listening through the Squeezebox; don't use the Sony as a cd player much at all anymore (although I do use it's analog outputs for two channel SACD playback). I usually leave the Paradisea on, because I agree, it's nice to just fire up the music whenever you want from across the room! Haven't had any problems with that so far.
I had a DAC Magic as well and for the price it's an amazing little DAC. Ultimately, I like the Paradisea much better because there's a certain smoothness and "reality" to the sound that just didn't seem to be there with other, upsampling DAC's. I'm still not 100% sure if that has to do with the NOS DAC implementation or the tube buffer stage, but I know I like it! I currently have a Raytheon tube installed that works great, plus an extra in reserve. I'd like to update to the Havana somewhere along the line and give it a spin.