Jdlynch can offer the best input here!
He evaluates the high quality multichannel analog stage of the lexicon as superior to the digital + analog of the marantz.
What he does not address is the value of room correction in his setup. The killer question is what is his room like acoustically and will bass management help or even be needed. Perhaps he has an ideal room and his bass management needs are trivial and so he really can't offer much. Perhaps, the Marrantz and full DSP never quite matched the Lexicon?
Finally, how does jdlynch (or anyone really) listen for optimal bass management... do you focus on your Two channel listening... OR do you evaluate the sound listening to multichannel blu ray sound.
For instance, if he is judging the marantz versus the lecicon on the basis of two channel music without a sub...
that might not be what you are looking for (opinion wise)
For example, your mains could desperately need the sub for that low base extension for music.
You make the point that your speakers are revealing... I read that as the speakers and your room are revealing.. what I don't know is what that actually means to you... (base extension, smoothness in the mids to highs, imaging, and all of those acoustic signatures) As you optimize the value in your upgrade choices... consider your gold standard.
IMO, the gold standard becomes a discrete two channel system with full range speakers in an acoustically treated room for the vast amount of music. Adding a video display changes the acoustics and so you start making compromises just by adding the flat panel. So, what tradeoffs make sense for your room and budget as you add in the other components given what you currently have and want to keep .... this is great fun!
I suggest you keep asking questions of others and yourself.
The great mystery to me is the value of room correction versus how your speakers perform and the nature of your room.
I am always looking for some wisdom here... Sadly, I don't have the budget to experiment for my self (sigh..... grin)!
What I follow is the advice that assuming you have good full range mains.. then you are best served with a discrete two channel system with HT bypass and then add an AV receiver or processor for the HT.
Then of course, you start looking at the other boxes you could add... (Analog Turntable), Music streamer, PC media server for high res music, Stand alone DAC cabled to your network, DAC wireless to your network. What about multihchannel content on your Media server...
My practice is... I tend to not punch in blue ray disks (hardly ever) .... and don't care enough about the video/sound to do more then watch the HD cable feed and plain vanilla 5.1 on movie content. I care a lot about the two channel music tho.