It was the output tubes all along...

@peter_s I purchased my 170s from Vivatubes.com. and had a good experience. 

@mijostyn I would like to try them again.  My initial audition was with the KT-88s and I found them to be somewhat anemic.  When I talked with Kevin about tube options, he was surprised on my take of the KT-88s and opined that perhaps they were past their prime.  I have a very open mind about trying them at some time.  In terms of the Swarm, I use the Dayton SA 1000 amp and bypass the internal crossover.  I spent a lot of time talking with Duke LeJeune about room placement and settings.  Low end isn't a problem in my estimation or others who have heard the system.  I'm sure there is room for improvement though. My crossover is set at 40.  I listen to vinyl predominately.  Nottingham Space Ace with platter upgrade and Van den Hul Crimson Stradivarius. I think this combo outperforms its weight.  Have order in for MSL ultra eminent x.  

@Lewm  I spoke with Kevin at VAC prior to the Magico purchase and he felt it was a good match.  I agree with him.  

@Mulveling.  I would try the KT 170s before the KT-150's.

@orthomead The KT 88s are more crystalline for lack of a better description. With proper subwoofers they will really sing. You have a fine turntable. Do you listen to any digital sources? By proper subwoofers I mean a subwoofer system that can be crossed at no lower than 80 hz and be able to put out a 20 Hz test tone at +10 dB from your loudest listening level  Duke has a fine system, but I am afraid it is a bit lost under S7s. Your VAC and the S7s will be A LOT happier if they do not have to deal with low bass. Separating the low bass out allows you to add the proper amount of gain to approximate the kind of bass you get at a live performance. Do you listen to any organ music? 

A system that is ruler flat in a residential room sounds awful. It will be way too bright and almost bassless. The right curve for this situation that most of us find ourselves in has 20 Hz at +10 dB over to 40 Hz at +10 dB then down to 0 dB at 100 Hz. I like a little 1 dB dip after that to 150 Hz, but that is personal preference. It makes the bass a little drier. From 100 Hz you go flat to 1000 Hz then start a slow taper to 20 kHz where you should be down between 6 and 12 dB. The louder you listen the more pronounced you want this. Every recording has a "right" volume, the volume it sounds best at. Too loud and it gets harsh. Too soft and it will be dull. 

If you have EQ capability you can force your S7s to do this, but the VAC will not like it at all. This is one of the two main reasons subwoofers are important. They are designed to make low bass and you can push them to the right volume without punishing the rest of your system. Even better is using a two way crossover to remove the low bass from the VAC and S7. The system will cleanly attain a realistic amplitude response at a volume that will make you feel as if you are at a live performance and I do not mean ear shattering either. To give you an idea, my speakers will not go as loud as your S7s. They sound bigger, but not louder. I use eight 12" drivers in four enclosures, each enclosure getting 2500 watts. Using fewer drivers would result in more distortion. Your Swarm has four 10" drivers. Two 10s equals one 12. Under a speaker that is capable of more output than mine you are using a subwoofer system 1/4 the size. 

Finances are an issue for most of us, myself included and Rome was not built in a day. You have a great start in the S7s, VAC amp and turntable. The Ultra Eminent is a super fine cartridge and the sweet spot in MSLs range. They are about to release the Signature Diamond for $15,000!  A good subwoofer system that matches your speakers will improve your sound quality eons more than a new cartridge. 

@mijostyn Thanks for taking the time and effort to help me improve my system.  I don't do any sound measurements, but it's clear that you have mastered the process. I actually believe everything you are saying.  Initially, I was entertaining purchasing the Magico subs until I saw the financial damage that would be incurred! What was presented primarily then by Mike was the Titan series.  The size and pricing for 2 units didn't make sense at that time.  More importantly, my overseer and CFO felt much more strongly than I did on that matter.  The swarm was an attempt to add something at a low level of risk.  I think I got my money's worth out of them, but I suspect you're right about them being underpowered for the S7's.  It would be great to be able to do an in house sub audition, but I don't think that's easily arranged.   We had an art dealer for a while who knew our house and interests verry verry well.  He would occasionally drop by to show us a piece.  He would do a quick walk through, rearrange some art and leave a space for the piece he brought over and told us just to "live with the piece" for a few weeks and see what we thought.   Oh, if I could only do that with subs.  The S series may be the ticket though. 

In answer to your questions, I have an old Sony SACD and Meridien cd player, but they are over 20 years old and don't see much play.  Meridien died and I don't see the benefit of a repair.  I should have Modrighted the Sony.  BTW, I have a TON of cd/sacds.  I don't have any organ music recordings, but I see where you are going with that. Thanks again for your suggestions.  You definitely got the sub gears whirring in my head.

The issue for many audiophiles is digital phobia. They stubbornly want to keep their system pure analog in the belief that it sounds better. In reality the benefits of moving over to a digital preamp/processor are legion. Conversion to and from 24/192 digital is now invisible. Once you are in numbers you can do almost anything without added problems such as subwoofer management, EQ, room control and high resolution steaming (Qobuz). The benefits for outweigh any detriment if there even is any. The best digital preamp for you would be the DEQX Pre 4 which is still in Beta mode, but the prices are still about 1/2 of retail. My friend with the S7s just got one. We have not set it up yet. The best value is the MiniDSP SHD. Down the line you can add a high end DAC for your VAC amp/S7s. The SHD is only 1500 with the best microphone. Add two Martin Logan Balanced Force 212s and you are in business for a total price of just over $10,000. The 212's are handily the best value in subwoofers today. With the SHD you only need a CD/SACD transport like the Bricasti M19. The SHD is set up to stream Qobuz which IMHO is the very best streaming service. It also uses Dirac Live, the easiest room control system to set up. My guess is that this addition will blow you away and you will wind up getting the DEQX which matches the quality of your system. It also has a fine phono section in it designed by Dynavector. It is designed to use a transformer for low output cartridges. I have a Pre 8 which is the identical unit , but with a 4 way digital crossover for people who want to triamp their systems. You can make any loudspeaker fully active. I would leave the S7s alone in this regard. Magico knows what it is doing. You want the Pre 4 which is somewhere around $7000 now and will retail for $10,000 I think. This would make adding subs a total of almost $20,000, but you won't need to buy a better DAC. Financial advisors always think HiFi is a waste of money. I do not bother mine with it avoiding the argument all together.  

When did this shift from rolling output tubes types to digital EQ and sources?

Anyways, I do agree with @mijostyn that a good ADC + DAC conversion process can be extremely transparent. Rather shockingly so. I’ve heard this by playing my vinyl setup through a Meridian 808v5 CD/preamp/DAC (which converts analog inputs to digital). I’ve considered continuing to use it this way for the excellent L/R balance control. Don’t mind the sacrilege. Still vastly prefer many of my vinyl records to their digital versions; it comes down to the mastering.

I’m surprised you find the need for subs at all on S7’s! They’re beasts, and rated down to 20Hz on their own. For music, no more should be needed, unless it’s some massive room? Adding extra energy down there will also add to the challenge of clean vinyl playback. You definitely DON’T want your VAC amps dealing with any subsonic feedback or rumble - it will rob their performance more than extension gains. Have you tried running the S7’s alone lately? Make sure you don't see any woofers flapping during playback.