How to amplify four 'front- speakers

I agree the Adcom will work, however you must keep the "protection" on when using both pairs of speakers, or the load on the amp will be 2.7 ohms as mentioned in the first response. This could eventually result in damage to the Sony. Here is another solution,

http://www.monoprice.com/products/product.asp?c_id=109&cp_id=10903&cs_id=1090307&p_id=8231&seq=1&format=2#description

This will provide proper impedance matching, and also give you volume controls to balance between the two pairs of speakers. Once the desired balance is achieved, then just use the main volume on the Sony.

Even with your current setup, the impedance selector switch on the back of the Sony should be set to 4 ohms. Sony must be turned off when changing switch position.

I think you need a multi-channel (4?) amp. There's no way that Sony is driving the B&Ws properly. Ignore the supposed wattage specs of the receiver. The Adcom speaker switch box is OK, but I'm not big on Adcom amps.

Well, I grabbed an Adcom GFS6 from eBay so will see how that works. I got the 6 instead of the 3 as i want to send music into a number of different rooms.

I'll report back on how this works...and thanks for all the helpful replies!