Add a preamp if you want to easily switch between more analog sources, but other than that, DEQX is already a preamp with remote volume control, so you should try to fix whatever problem you have within the DEQX rather than paint over with tubes, if that's what you're thinking. You could also just add a simple analog input switchbox before the DEQX. You could make it yourself, or buy from finished unit from Goldpoint.
If you are inserting a preamp to fix the sound of the DEQX DACs then I think you are better asking DEQX tech support to help your fix it, or even hire them to fix it for you. I have heard quite a few DEQX based systems and they are consistently awesome tone quality when setup up correctly. I have never heard any problem with the output DACs, even on older versions playing on RAAL 5" tweeter. But the setup of those positive experiences has always been done either by experienced DEQX user Rick Craig or by DEQX tech support themselves. When it is setup by inexperienced users the sound is always compromised.
If you are just looking for transparent signal switching and volume control, I don't think you can beat the new Bent/Slagle preamp. If you want to add some phat lovin tone, look for 6SN7, like DeHavilland Ultraverve. These both are universally loved and good value, with good resale.
Have fun V! and good luck with the move!
Rich
