Not looking to sell my SDE300 rack units, but wanted to chime in regarding a different point.
If you are just looking to run Mono, then disregard this message.
But I will tell you what happened to me, and how I ended up acquiring multiple units......Wet-Dry-Wet, happened,

.
Anyway, I am still a huge fan of all of the rack gear that I used back in the day, and also a lot of the stuff that I could not afford back then, when I was only focused on "eating, playing, and sleeping".
If get 1, you will want 2, and that could possibly turn into a third one. And they are harder to come by, at least affordably, these days.
Look into the new Boss SDE3000-D or the SDE3000-EVH pedal, if you are interested in Dual delays, Stereo, Wet-Dry-Wet, etc. It is my understanding that either of the units, can be programmed with Left / Right, on each side of the dual delay pedal. True W-D-W would only be possible with the EVHunit, due to the available outputs, but the 3000D is capable of doing 300ms, 600ms, and then 900ms on the opposing side......which sounded pretty good on the Leon Todd video that I watched on YT.
I ordered one, but have not done a deep dive on it, due to my work schedule lately. I do know that it is not much different, and is in some ways BETTER, than my old rack versions of the same circuit (ie. Tap tempo, everything in one unit, etc).
Sorry for the long diatribe, but I am fairly impressed with this unit so far.