Where to insert tubes while running a Luxman SS integrated

I've recently upgraded my integrated amplifier from a Cambridge CXA81 to a Luxman l-507uxii.  The Cambridge is definitely not bad for its price, but the Luxman is a different animal and is making me want to upgrade everything else in my system.  Which brings me to my point of discussion: I'd like to insert tubes somewhere in my system to get some additional warmth and a more holographic soundstage.  Would adding a tube preamp and running the Luxman as only a power amp be best to do this, or would it be better to get a tube dac for my digital, and separately, a tube phono stage for my vinyl?