A switch for 3 amps

@OP , to clarify: You want to switch amplifiers, between (line) pre-outs and speaker (load) outputs of 2 amps to one pair of Maggie’s....Douk Audio "LITTLE BEAR" VU3. the Fosi LC30, NeoHipo ET30...all seem to have sprung from the same source, kinda.....but do essentially the same thing: A or B amp to A or B speakers.....VU is a ’classic touch’, but having owned a tiny box with LEDs’ did that as well as the ’power’ function which was a ’good to know’ thing...

There’s a VU control for that, but wonder if it’s switched between the 2 functions of the meters? 🤷‍♂️

It was interesting knowing that the bulk of ones’ listening levels was at 1~10 wrms, whereas the peaks would briefly peak higher....

At least, getting some specs with the Fosi is easier, mho....

My personal switching routine is somewhat different...

@audiodidact -- concerning your question, about 18 years ago I had Maggie 1.6QR speakers that I powered with rebuilt Dynaco Mk 3 mono amps (60 watts each) and was very comfortable with the pairing.  No problem with volume, though I'm not a head banger.  I had a good sized room (approx 25' X 16') and my typical "serious listening" volume would have been 85 to 90 dB.

@mlsstl —That sounds really encouraging.  My  1.7is really are not very different in impedance and sensitivity from your old 1.6QRs and the fact you ran them with 60w monos successfully is music to my ears.  I generally listen in 75–85db range, not so loud, though when I want to be crazy I will turn it to 90db max, depending on the source material.  I’ve modded the Maggies with new crossovers from GR Research and with my SS amp, the 400w 4ohm Parasound A21+ , the Maggies can really sing as loud or as quiet as I want. So,  I’m hoping that, as a result of the improvement the Maggies will be even more accepting of the lower watts from the tubes.  We’ll see. I will keep the Parasound and add the mono tubes with the Luxman switcher…unless, the Quicksilvers deliver a better sound at “serious” listening levels.  All the amps will feed into a Prima Luma 300 preamp which as sold me on tubes. In fact,  I’m so sold on tube monos now that if the QS can’t rise to the occasion, I will just save a bit longer and get higher wattage tubes.  This is all new territory for me so I’m very grateful for all the input!  

Lucky for you I have been down this rabbit hole and search to the depths of Google far beyond I ever imagined.😁 I have found a whole bunch of solutions for your exact needs. However I am going to list all the ones I have found and you can pick out which one you feel is best for you. The one I like the most out of all of them is a company from Europe that will custom make exactly what you want based upon your needs. Rather than try and fit in your requirements to a pre-made box you have a box made for your requirements. 

This was the first stage of a setup for me and now I am looking for a digital version that will run USB to a USB switcher source and that is a whole another mess I am running into but that is a whole nother set of problems for me.

#1 Choice, they will build whatever you needTake a look around at site it's pretty fun​​​​​​​ their products.https://vintagemaker.net/

A lot of these are XLR but you can get component or RCA to XLR cables and I suggest to use Amazon and don't pay for anything expensive as it will not make the quality any better.

#2 LinkBone 8×8 Matrix XLR switch

#3 Black Lion Audio PBR XLR Patchbay\

#4 4 In 1 Out Stereo Audio Switcher Switch Splitter Selector Balanced XLR Interface Remote Control VFD Screen

#5 Kramer VS-4X 4x1 Balanced Stereo Audio Switcher (XLR)

#6 XMSJSIY 6.35mm/3.5mm Audio Selector Switcher 6-in-1-out

#7 Nobsound 3-IN-1-OUT XLR Audio Switch

@audiodidact Did any of the solutions I mentioned fit your needs. I haven't put together my audio room yet but one of those options are going to be in my audio room and it's more than likely going to be the vintage maker as I think I'm going to go with something custom made for me. However there is a lot of decent Solutions there from cheap to expensive. But I do like the vintage maker and he can custom build me what I need. 

I'm more or less need the same thing but for a USB in and USB out I don't know if this guy can build what I need but I might try him for it. Not sure cuz I'm looking for something pretty special to you and have not seen what I want so getting it built might be an easier way but basically I want to be able to choose which USB source and choose which USB DAC. So I would be able to pick between 5 to 6 different sources and choose between five to six different Dax or apps to send the signal to. 

I'm going to keep an eye on this page and see how you make out with it please keep us up to date there's not too many forums where I've seen anybody really do what you want to do and what I want to do. A lot of people just kind of abandon the forum post's and never follow through with what happened afterwards. I figure there's probably a lot of people searching , Well I know there's a lot of people searching and so far actually I accumulated the best list of switches for amps. 

Now I think it's just a matter of me and you and other people trying them out and finding out what works best.