I play with a real tube amp, as it happens about ten feet away. Can’t abide daily practise with headphones, I like to feel the air move in the room, it’s all part of the interactive experience of playing the electric guitar for me. So let’s say 10ms latency as sound travels through the air. I did some tests last year with guitar DI into PC with amp sim software to stereo monitors (also the same distance away), with differing buffer sizes, and I start to notice the added round trip latency at around 5-6ms (so 15-16ms total, acoustic and A/D/A latency), and it starts to negatively affect my playing, particularly single note lines. Adding an extra possible 12ms of latency to the 10ms acoustic latency by using the H90’s two inserts in series, and you’re talking a whopping 22ms total. It’s not unusable, but it’s not ideal either, for me at least.