How to make a preamp bypass switch?

I love my Sony TA-E 80ES preamp - Hafler XL 280 amp combination, but notice a more transparent open sound when I run the outputs from my Oppo BP 83 straight to my amp and control the volume with the Oppo remote. I need to keep the preamp in the system to play vinyl, but am imagining that a switchbox with a really high quality selector could be made (or perhaps is available) which has seperate inputs from the preamp and the Oppo which could be used to choose which input would output to the power amp.
The Sony has a "Direct" switch but the signal still has to go through the volume control circuit.
The gradation of sound using the Oppo volume control is not as gradual as a preamp volume control provides, but it is adequate and the transparency gained is significant.
Has anyone out there tried something like this? Any input on whether it is feasable? All ideas would be appreciated.

Thanks in Advance
A good pasive preamp would do this and have a better volume control than the Oppo.
This box does exactly what you need, is expensive and has a distinct high end look to it.

If it is any good I cannot tell, but I would expect no audible degration from the box itself. In a real high end system you will hear some loss from the extra pair of cables. An alternative would be to ditch the sony, get a preamp with a true bypass (not unity gain), and run the Oppo through the bypass.