I had an 830 and today have an 861 directly connected to a FPB300. The 861 would be best, but I bought it used for 4500$, and it will still be above your limit. One of the advantages of the 861 is that the sound does not degrade that much with lower digital playback levels. All the older models show more significant degradation of sound if you use the digital volume control to lower the volume by 20 db or so.
Try to get an 860x to fit in your price range (may be difficult). The 860X is much better than the 850. Honestly I think that the 850 is an 830 with the chassis of the 860 + a more expensive transport, that's it. You only get the look and feel of the more expensive 860, not the sound. By the way the 830 it a great sounding unit, so is the 850 - just more expensive.
Hope that helps - Uli
Try to get an 860x to fit in your price range (may be difficult). The 860X is much better than the 850. Honestly I think that the 850 is an 830 with the chassis of the 860 + a more expensive transport, that's it. You only get the look and feel of the more expensive 860, not the sound. By the way the 830 it a great sounding unit, so is the 850 - just more expensive.
Hope that helps - Uli