Marantz is a good choice. LPCM over dolby headphone will work according to my experience with the SR7002. It's fun and I use it for DVD movies and games. That said, you need to know that the Marantz line does not have the processing power to both decode HD, like TrueHD, in the reciever and implement Dolby Headphone. i think you said you'd use LPCM, so it should not be an issue.
The interesting thing is that i switched back and forth from LPCM and bitstream and discovered that while I enjoyed the frontal sound of speech with Dolby Head on, the bitstreamed stereo downmix actully trumped it. I heard seperation that was surprisingly good, and details were better. I don't remember feeling this way about non-HD over headphones, so I'm not sure what's going on here. It may be that i prefer bitstream to begin with (I do think it sounds better). But for LPCM dolby headphone should work just fine. I have Senns HD580, so I know where you're coming from. The Senns are really great for picking up the nuances of 3d sound, even when downmixed into stereo. The 595 is probably even better for movies. Only downside with the Marantz pairing is the Senns would prefer a brighter match. Not a big deal as I'm being picky. Anyway, i hope that helped.