zilbermm,
I don't know why Zone2 is not a reasonable option for you. If this is for 2-channel music (CDs), then Zone2 with an analog connection should work fine, unless you want the subwoofer to be in on the action. Just assign an unused analog input ("CD", for example) to Zone2. I doubt you can tell a real difference between decoding with the player versus decoding with the receiver. Just make certain you turn off the "bi-amp mode" to use Zone2.
Another thing to consider is that some receivers, when in "pure direct" mode (or something similar), will not apply bass-management to the front speaker outputs and instead will send a full-range signal to the front speakers. The receiver's settings are ignored. The subwoofer is either not utilized in the receiver's "pure direct" mode or if it is still utilized, can usually be set to off by turning the sub's level trim down all the way until the receiver's display says "OFF". Most receivers remember the settings for each mode. So, if you had an A/B speaker selector switch that allowed you to switch between the the KEFs and your towers, you could take advantage of this if your receiver operates this way. What receiver is it?
To take this a step further, if your player has more than one digital output (i.e. coax and optical), you could use one connection specifically for your music playback by assigning that particular digital connection in the receiver to, for example, "CD". Then you could set the receiver to use the "pure direct" mode when "CD" is selected as the input source. It should remember this setting. You would still have to have a way to switch off the KEF speakers, and a speaker selector switch would be the best way to accomplish this (as opposed to trying to use the receiver's "bi-amp mode" + a switch). If your player has only one digital output, then you could still set up a scheme like this but you would have to use an optical switcher or cheap video switcher (depending upon what sort of digital output your player has) to split the digital output into 2 signals, one of which you could assign to movies and the other to music.
Yet another option would be to use an advanced remote controller such as a Harmony. You could then program it to switch the front speaker settings to LARGE for music listening and back to SMALL for movies. Again, you would still have to use an A/B speaker selector switch, but if it was remote controllable, you could program the Harmony to do this, too.
But, for what you want to do, utilizing Zone 2 is your best option.
Since you have to have a way to turn off one or the other pairs of speakers, the other options I discussed would require an A/B speaker selector switch but would still not require you to utilize the receiver's "bi-amp mode".
