The Lexicon MC14/Bryston SP3 is a nice sounding unit, but it has a very laid back style of sound. I think it's a combination of the digital board and the slow slew-rate Class A circuits. It could also be that there are no localized power supply filter capacitors directly at the circuit. It is a massive power supply with a couple of 100uf post regulator caps and that's what powers both the digital board and the analog sections.
The Krell processors are more forward with a lot more attack in the sound. Definitely more exciting for home theater. However, the Krell doesn't support atmos at this time. One of the things I like about Krell is that they use linear power supplies for all circuits, including digital. Many processors will use linear for analog, but then use a switching power supply for digital. The Krell Foundation 4K is the only thing current right now.
The Marantz AV8802A (or even AV8805) is a very nice unit. It has a very good size main power supply (larger than the Bryston). It uses a rather slow op amp for the DAC I/V section, but Marantz has a lot of localized capacitors in the DAC board. It also has very good power supply filters on each of the individual discrete analog output boards. I would put the Marantz as a serious contender.
The McIntosh processors are liked by many. I believe it uses all op amps (no discrete circuits), but they also have very good power supply sections.
As far as Marantz vs McIntosh, it's difficult to say which would be better. Marantz can be sold for a cheaper price because they have a massive distribution and sales network, so they can re-coup investment easier. The McIntosh are not going to be sold nearly as much as the Marantz, so the cost is significantly higher. It's hard to say what would sound better. the McIntosh definitely wins on front panel and asthetics. though, I have heard that their processors are buggy and that McIntosh never fixes firmware.