You can buy high level to RCA converters mostly anywhere; radio shack even. Then you take the factory wires going to the speakers (or to the stock amp; which will bypass the stock amp) and then RCA to your new amplifier) But thats a pain.
I know the avalon isn't that great for aftermarket HU's, but that'd probably be the best solution
I know the avalon isn't that great for aftermarket HU's, but that'd probably be the best solution