Tube or solid state phono stage?

I agree with @knotscott, there are good (and not so good) examples of both topologies. Generally speaking, good SS phono stages can be had at moderate cost. If you want a quiet and dynamic tube phono stage, the cost of entry will go up. At least that's been my experience.

The ARC Ref Phono preamps are quiet and transparent - not tubey at all. Your Ref 6 will sound great with a Ref Phono 2 or 3.

As a very general observation:  if your tube system is in danger of lacking good dynamics, something is wrong.  At moderate to low volume levels, I expect tube gear to sound considerably more dynamic and alive than solid state.  As a more specific observation, your particular tube electronics is on the leaner side, not the warmer side, of tube electronics; for my taste, I would want a quite warm sounding phono stage in that setup.

I have heard, and liked phono stages from Lector (Italian, tube) and Audio Note (requires SUT for MC, very expensive), Allnic and Zanden.  I own the Italian Viva Fono myself.

You won't go wrong adding another AR piece to your system.  That would be the first place I'd look in your position.  

@big_greg,

I've never thought about adding AR to my system protection!