John,
I've had a 570 since shortly after they came out, and I didn't know about
holding the notch button in for a different setting. I tried it, and it does
indeed make a difference.
Kevin, I don't think there's a separate receiver antenna connection. I
haven't used a 2000, so I can't directly compare the two rigs as you
outlined. But, I find the 570 receiver adequate for my needs.
Mike, K5XU