Switch for 2 preamps to 1 amplifier

I want to know if there is currently available a high quality switcher for connecting 2 preamps into 1 amplifier.
My dilemma is: I own the original Krell HTS preamp which digitizes all analog inputs, I also own a Marantz PM-17 for my 2nd zone. I would like to take the preamp out from the PM-17 to a switch so I can hear my dac's in my cd player instead of the Krell - this switch would output either the krell or the Marantz to my Aragon 4004 MKII.
If there is not a current consumer switch available is there a custom unit someone may have designed (using Cardas rca's or..) and if so what type of switch should be used for this? Please Help -
You could run the pre-outs from the Krell to a tape input on the Marantz. Then the pre-outs from the Marantz would always go to the Aragon amp. Use the tape monitor on the Marantz whenever you want to hear the Krell. This is a quasi-HT bypass setup.
Why not connect the L/R output of the HTS to an input on the Marantz? A HT bypass input would be ideal.
Nighthawk/Kr4: thanks for the great input! (no pun) - I will try this as a temporary setup to determine the sonic difference from my CD dac's. If I were to want a permanent setup I think I would prefer a direct switch (clean and beefy of course) and this is only due to not knowing the true circuit path my Krell would be enduring thru the Marantz - does anyone know if trapsing my Krell thru the PM-17 is a clean or dirty circuit path? Thanks, Chris