Which to keep! Pick one of these two soeakers

The previous owner of the Martin Logans had them bi-amped with an Audio Research VT100 (feeding the subs) and ADCOM GFA-555 (feeding the panels). The Audio Research SP16 preamp feeds both amps. I have all of this gear now but I’m only running the VT100 biwired to both the panels and subs in parallel. The room is carpeted and about 12x20 or so. I’ve beed auditioning the Spendor and ML with the Audio Research pre and tube power amp.

Your opinions are super helpful, there are little bits of information mixed in to each that helps me piece together some of the greater experience you all have with these types of speakers. To those who are a little rubbed by me asking for the experience and opinion of others, I find it extremely helpful, and it helps me to bring attention to things I may not have otherwise consciously been able to consider in my decision. It also adds confirmation to the experience I've had, or helps me reconsider things that maybe I got wrong. There have been many useful points brought up here. 

I mainly bought this guys system for the VPI turntable, Audio Research pre-amp, CD Player and VT100 MKIII power amp. Those three items are nicer than the core of my #2 listening room that is also my home studio. There was a whole bunch of other stuff in the rig like a transient noise reducer, the Adcom amp, the speakers. I was initially thinking I'd sell the speakers but they turned out to be pretty nice which is what got me into the predicament of considering my Spendors for replacement. I wonder if I could fit both sets of speakers and wire them to an AB switch. They are different Ohms though, The ML are 4 ohms and the Spendors 8 ohms. I wonder if there is a way to wire them up to a couple of switches and turn off one, turning the other on. 

There was a Marchmand EQ and a Marchmand tube crossover also hooked up to this system that got sold out from under me. I would have really liked to have those to play with on this setup. That may have helped a lot with the Martin Logans. I feel they need a little high rolled off at times from what I'm hearing, maybe the lows bumped just a tad. Same with my Spendors, they are really bright but I really like the clarity 99.9% of the time. I have a sub that I use to fatten the room up. 

Is there a good EQ that I could invest in that ya'll would recommend? I really liked the Marchmand controls, it was 5 knobs and pretty simple and seemed well built.

@loomisjohnson my spendors are below 1000 serial number and are probably pretty old. I'm not sure how many they made in the 70s/80s but it would not suprise me if they are pre-1990. I wonder if I rebuild the crossovers if they might sound a lot better on the lower register. It's possible that the crossovers are out of spec and not pushing enough low frequency down to the subs.

@kennymacc @mirolab The experience of others with the same speakers is just a factor in my decision. A wise person is open to the experience of others. A fool makes decisions in a vacuum. There may be people who have had each of these for decades, they will know things that I will not know in a only the weeks I’ve had each of these. Space restrictions for forces me to choose one pair quickly.

@newbee so it turns out that the Adcom is actually a totally rebuilt dual mono Musical Concepts creation. I found the docs and receipt for the work and sure enough the device is gutted with some amazing work inside. So the guy was powering the panels with this solid state creation and the subs with the VT100 MKIII tube amp. I could hook it up the same but I'm now missing a way to balance the signals. I need a way to control how much signal goes to the Adcom vs the amp for the subs. 

@newbee  honestly, I had high hopes for the ARC VT100 but I'm a little put off by the extra heat it puts off around my wood Rigidrack. Kind of makes me nervous but maybe not an issue. Right now I have a McIntosh 4100 + Adcom 555 hooked up and the ARC is out of the rack momentarily. I have the MAC hooked up to the panels and the Adcom on the woofer. When I crank up the preamp to about 70% I can blend in the desired amount of upper register on the Mac and I also have the EQ on the MAC. I have to say it is very useful but I wonder if I just downgraded by pulling the ARC out of the rack. I had initially planned on selling the MAC 4100 to recoop some of the money I spent on this system's various components. I can get $1500-2000 for it on eBay.

@newbee Both amps sound good, the ARC sounds maybe a little smoother like you said, a little more organic while the Musical concepts is a little cleaner and in your face. Both sound really good though. One thing to consider though is that both sets of these speakers are having issues with low end when bi-wired. Each sounds much better when you push more low end to the subs. The upper registers sound much better on the Spendors, much more texture and guitars/horns sound incredible and detailed/alive. The ML are a little more piano like in the upper registers, seems like a little air is missing that is in the Spendors. I might try running the amps bi-amped, if there is a natural volume difference between the two amps maybe I can use that on the bass side to push a little more low through the speakers.