Lonson is correct, only those new to the high end, home theater setups, or someone really lacking space, would stack them in the first place.
One of the many advantages of monoblocks is being able to place them very close to your speakers. That way you can afford to use a better quality of speaker cable. Instead of needing 8ft or more, you can get away with under 3ft.
You really have to give up on this need to have it verified by members of this forum. Robert Deutsch has written about his results. If you have trouble hearing the difference, it may be that you stuffed one behind a big TV. Take a look at any pics of a high end system with monoblocks, and you will see both setup on matching stands, or wood slabs, maybe even on the floor with cones under them. But they will be both setup the same way.
I don’t know anything about your setup, your room, or decorating requirements, but if you were able to build a custom cabinet, consider building two identical amp stands. Something like Mapleshade or Timbernation would sell, and place your amps behind or next to your speakers. That would be the best overall solution.
Then stop listening to the amps, and listen to music. Many of us became “audiophiles” because of our love of music. We wanted to hear our records at their best, so we bought better stuff, then, as finances would allow, even better stuff. And while I would like to upgrade a few components, I don’t dwell on it. I choose a record, CD, file, data stream, or a college radio station, and I listen to the music. If you are lucky you get to a time or setup that allows you to focus on the music, and forget about the gear. The only time you want to be listening to the system is when you are making changes, or comparing something. Listening to music will bring joy, listening to the system will have you wondering “what if”, and there is no joy in that.
Here is my recommendation, go put on some music you love, close your eyes, and listen to the music. Focus on the vocals, the lyrics, or the primary instruments, I had to stop writing, Tom Waits was speaking to me, man that sounds good. “A Christmas Card From A Hooker In Minneapolis”. He’s about 12ft from me, if I close my eyes, it is just like having him in my listening room. Ah music, it’s a wonderful thing!