My Vali 2 is here!
It hasn't been on for very long, so my impressions might change, but as of right now with the 225e here's what I'm noticing:
The sound is a little more crisp and clear, with slightly better instrument separation and definition, and maybe the soundstage is also a teensy bit wider than on my Geek Out V2. We're talking degrees here, not feeling like I have a whole new pair of headphones or anything.
If there's one downside, it's that I feel that just a bit of the energy is dampened, but I also noticed that songs that were feeling peaky before ("Going For The One" by Yes for example) are much more manageable through the Vali 2.
I have ordered a different current production tube to try with it, and I'm eyeing some relatively inexpensive NOS tubes as well. I'll report any particularly good synergy if I hear it.
If you're currently using the Grado without a dedicated amp, the Vali 2 will definitely be an improvement. If you already have an SS amp and want to try tubes, the Vali 2 is an inexpensive way to do it and sounds good with the 225e. If you already have a decent SS amp and think the Vali will be a big step up, I doubt it will be, unless your SS amp is simply a bad match for the Grados.