Do not try to run an amplifier from the speaker outputs of your receiver; the power output is far too high and will most likely destroy the input stage of the amp. The input stage of the amp needs a signal with just a few volts, the output from the receiver probably exceeds that 10 fold or more.

There are speaker level too line level converters you might consider if replacing the receiver is not an option.
http://www.hometech.com/audio/spline.html

Regards

Those who have long enjoyed such privileges as we enjoy forget in time that men died to win them.