The 897 has audio level DSP, which in a nutshell, works after the signal has been converted back to the original, intended information. Any interference that was added in the "rf domain" is still there. Audio DSP attempts to simply do what a skilled operator was once forced to do -- ignore what they didn't ant to hear in favor of the intended information. It can work well under certain conditions but it does little to help in a contest environment where there may be many stations operating close together.
The 450, 950, etc., use IF DSP, which occurs after the signal from the antenna has been knocked down in frequency a bit. The imprtant thing is, that it's operating on the signal in the rf domain, so it addresses all the stuff that's actually happening on the air, that is causing interference. The caveat is that it requires faster processing and careful design to minimize distortion by the DSP itself. Some radios have both.
If I were setting up a dedicated fixed station, I'd definitely go with something like the 450, 950, or better yet, an Elecraft K3 (one of the best amateur receivers availabe), or a TenTec Orion. My choice of the 897 was driven by limited space and the need for a radio that can "do it all" from 160m to 70cm.