I had the 1200 and sold it to help finance the 3000. I found it to be a capable radio. I have the Icom 7410 and find that to be a fantastic radio as well. Of the three, the 3000 would be my choice especially considering it does FSK RTTY, which many prefer over AFSK, without the need for anything externally other than the USB cable.
The Astron is a great choice. I use a couple of Samlex SEC 1235M units and they've been chugging along for a few years.
As for the 1000, it was a great radio back when, but I suggest taking a look at Sherwood's receiver test data page. It has some value, though it shouldn't be used as the only reference for a decision. Regardless, the 1000 is well behind the 3000. You might also want to consider the Kenwood 590SG.
Other than filtering, I don't know that you would realize a real difference between any of the above radios in receiver performance. I'm aware that the K3 is a great radio, but again, you're not going to magically hear something on the K3 that you can't on any radio in the $1,500 t0 $2,000 price range.
If you're really interested in a better receiver, consider putting money into a good antenna if you don't already have one.