How Best to Hookup Switchable Multiple Preamps to a Single Turntable

I would use the tube unit myself but @millercarbon is correct- with that sort of signal level a switch box will be detrimental. Just do the switch manually and things will actually be a lot easier.

Thanks much for the reply.  The reason I was asking is that I have a Pro-ject Tube Box S2 tube stage (with upgraded Gold Lion premium ECC83 tubes installed) and a Sutherland Insight solid state stage.  If I was in the mood for a warm tube sound for some recordings I could switch back and forth.  Am I crazy or should I just use the Sutherland stage?

You're asking if its possible to run a signal through a bunch of extra stuff and not lose anything. If you can figure out how to do that you can make piles and piles of money. Until then you will just have to either plug and unplug or use the tape mon and another interconnect.