Which to keep! Pick one of these two soeakers

@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. 

You need a passive attenuator of some kind between your pre-amp and one of the amps, probably the amp feeding the sub. I see them coming up for sale used between $400 and $600, but from my point of view I think what you might gain by bi amping these speakers you’d lose by all the extra stuff it takes to do it. I’d run them off one amp. FWIW, the Musical Concepts mod changes my opinion of the Adcom, but I’m not convinced that it is a better amp for the panels. My gut tells me the ARC amp should go to the panels and the Adcom to the subs. When you figure out how you will get the two amps balanced, output wise, try switching them around.

@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.

Just for fun, humoring me perhaps, just try running the speakers full range with one amp. First the Musical Concepts then the ARC. Listen to the 'sound' and the differences you get with these amps. I suspect that tonally speaking there might not be a huge difference, but I think that the ARC will have a smoother sound than the SS amp. I don't know what your 'rack' looks like but you can deal with the ARC's heat by either putting it on the top of the rack or placing it on the floor next to it. For sure make sure you give the amp a lot of free space around it. 

Sell that Mac and the 555. Neither, in my estimation, has the 'quality' potential of the Musical Concepts and ARC. 

@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.