The first avenue that comes to mind is railpace.com, the on-line site for Railpace magazine. Click on their "Interlocking" tab and you'll find a large number of Eastern links that might lead you to someone posting audio recordings. Oh wait, there was this outfit called Quiet Please Recording, which put out some fantastic stereo recordings on CD some years ago, many of them done in the Northeast. Look them up. I share your feelings about the sight and sound of high-speed passenger trains. I spent my teenage years right alongside the Surf Line in southern California, where San Diegans flew by at 90mph behind Es, SDP40Fs, and eventually F40PHs. I also spent nearly eight years living in northwest New Jersey, and had some memorable days on the NEC between Princeton Junction and Trenton. You're right; nothing else like it in the U.S.