Hide & move silently

[Aelcar]

Amplify's counter is the fact that you need to know there is a sneak to pop Amplify.

This is almost true. Amplify sure is a way to spot the sneak when you know there's a sneak around. But it's also a counter to being spied upon, being followed when you're intentionally going somewhere you don't want to be followed. You stop at a bottleneck of some kind, cast amplify and C/C and make sure there's no one around.

But indeed, these spells are 6sec/level spells, which means you can't just go around with them all the time.

A counter to be spied upon in that fashion, yes. Which is a good thing, in my opinion: if one wishes to spy, he or she has to do better than put up stealth gear and click the "Hide" button.

Incidentally, Alarm spell and closing doors do exactly the same thing.