My thoughts: The B&K are undervalued in the market. Krell is overvalued. Halcro is at the top 10% of the entire market. So, not really a fair comparison.
Krell HTS 7.1 was released in late 2001, early 2002 if I recall, at a list price of $8000. Much has changed since then......but still a nice piece.
The Halcro was released in mid-2006 if memory serves me, at a list price of 10-12K, depending on the configuration. Again a bit dated, but like the Krell, a nice piece.
The B&K Ref-70 is the latest processor for them, so you are getting all the latest in HDMI switching, HD-Audio processing, and a few other features you would not get in a 3 or 7 year old processor, at a list price of $3800.
If all were equal price, I would choose the Halcro, as it has great audio, and I would forgo the need for HD-Audio formats on BluRay.