Thank you! That's what I intended: ruling out one or the other and seriously thing about what remains. I couldn't replace everything even if I wanted to. So e.g. keeping with the Threshold sounds like a good idea. The Maggies sound weak to me after all these years, or maybe my taste has changed. I even get a fuller sound at my computer with the MM1 (they sound incredibly good!!).
Regarding the Revox, I have no idea what nowadays preamps produce, compared to it.
Your Revox dates back to the golden age. However it is purely analog and has no digital processing.
So the issue comes down to whether you want digital processing. In other words do you want subs and bass management? Do you want the preamp to decode digital streams, especially the new loss less codes, and do you want network streaming?
So far you have not fleshed out what you want to do.
It is really important for you to articulate what you want.
As far as the Magnaplanars are concerned, those older units are very bass shy. If you want good planar speakers, in my view your best option is the big Magnaplanars or the Quad ESL. The latter I favor over Martin Logan.
If you are in the upgrade mood do not exclude good monopole speakers.
We absolutely have to have a better idea of what you want.
If you click on my signature you can see a mix if older and new gear, integrated with a computer. I will probably add a rack computer for video and streaming and keep the current audio workstation for audio editing and productions only and take it off the NET.
As you see there are a number of older pre amps, four in fact. Three are used a LP and tape preamps, the fourth as an editing desk buffer amp.
By the way do you still have your LP gear and any analog tape machines? If so what? I'm assuming that if your gear is 30 years old you probably do.
You can avoid digital gear entirely except for your TV box, disc player and TV, but it takes a few work arounds to get it handy and work well.
Here is such a system.
So we must know what you want. If you don't know what you want, you need to ask some thoughtful questions.