Integrated Amp upgrade path


I’m currently using a Macintosh MC 8900 to drive Vandersteen Treo CT’s, with a six pack of Rel S510’s, streaming only.  I understand Boulder will shortly have a software upgrade for the 866 that will include an Air Play equivalent to allow full use of most streaming services.  Looking for thoughts from anyone with experience with the 866:  how much of an an SQ improvement with this upgrade?  Incremental?  Immediately noticeable?  Thanks for any help!
cosmic_charlie
OP, I notice you have a REL 6 pack. Currently I have 2 REL S/812s and am thinking of building up a six pack. How challenging was it to dial in the six pack?

Thanks
@hsw—Not hard at all.  I set levels and crossovers in pairs, from the bottom row up.  Crossover level is lowest for the bottom pair, second row a bit higher and third row is higher again.  Levels follow the same pattern from low to high, but are closer together.  Then after those were done, small tweaks to each row as needed.  I found the level control to be the most sensitive and it had the biggest impact, but it was not hard to match with the volume of the main speakers.  I have a small room (10 x 14), so YMMV.  Maybe an hour’s time, max. 
The line array concept was a big plunge for me, but the results are spectacular:  wider soundstage, bigger image, better clarity, and most significant to me, more heft/substance/weight (without any hint of softness) to the rendering of each note, tone, vocal, or percussion—across the whole music spectrum really, which to my ears has always been one of the hallmarks of live music.  Not a cheap upgrade by any means, but  the ROI is stunningly good. 
Thanks for the feedback!

It look me about a month to tweak my RELs. Mostly because I first went down the path of lower crossover and higher volume. The sound in my system was very clean, similar in voicing to the Revel Salon/Studio series, but that was not the aesthetic I was going for. I doubled back to try higher crossover and lower volume and I preferred the richness the higher crossover afforded. 
They will sound completely different so different that you will like one and not the other different so make sure where you buy the boulder has a good return policy if you do not like it because it is an expensive proposition to gamble on.
@arafiq my experience with the Node 2i was positive.  It's $600 with great features.  It was my dipping of the toe in digital.

When I upgraded my preamp - McIntosh C2600 - part of my reasoning is the internal DAC and phono stage (MC and MM).

I set up the Node to provide go through the DAC as well as provide an analog signal.  I would switch and do an A and B comparison and at times there was a difference.  Enough to make me wonder if there was value in upgrading my source given I upgraded the preamp/amp and speakers.   

So I decided to evaluate the impact of upgrading the DAC and compared the Moon 280D to the McIntosh internal DAC (version 1 non-modular) and the Node 2i

I was surprised by the improved details with very dense music such as Black Sabbath War Pigs and on songs with delicacy like Steely Dan's Hey Ninenteen or Chuck Mangione's Feels So Good on the Moon 280D.  It was significant over both the McIntosh DAC and the Node 2i DAC - so I decided to go for it.

I found the MiND2 easier to set up than the Node 2i (specifically with my NAS).  I've been impressed with Moon customer services support - they respond to questions quickly. 

Based on my experience, Moon is an excellent value for the money.  If I ever update my DAC/preamp/amp...Moon separates or integrated will be on my auditioning list. (in addition to Audio Research and McIntosh)

I like my McIntosh and I was able to buy it at a discount because they were demo models - I've heard Moon products with Davore Super Nines and Wilson Sabrina X speakers and I have been impressed.