Yeah, an amp with pre out is twice as much as the AM1. Even then, I can see only one below £300+ that has pre out. That did surprise me. Don't expect to see that on a sub £100 amp, but £200, you would think it would be commonplace.
Connecting the subwoofer to the amps speaker outputs wont have the amp driving the subwoofer. That would only happen with a passive subwoofer. Active subwoofers with speaker level input just use that for listening to the signal.
Connecting the subwoofer to the amps speaker outputs wont have the amp driving the subwoofer. That would only happen with a passive subwoofer. Active subwoofers with speaker level input just use that for listening to the signal.