I've been wanting to make a build that can sneak about, slitting throats and stuff, but also can hold it's own in battle when not sneaking. So, I've come up with a Heavy Armour build which heavily involves sneak but I wondered: is it possible to make it so Heavy Armour is nearly as effective as sneaking in Light Armour? I had a few ideas, like the Steed Stone, the 'Silence' perk and the 'Muffle' enchant but I wasn't sure what these things done or if they'd have any effect. Is it possible to sneak effectively in Heavy Armour, or is it a doomed idea?

Yes it's possible, with the right perks, skill levels, and/or enchanted gear and spells. I've gotten Sneak to 100 on several HA characters, I prefer the Muffle enchantment on my boots (provided I can find it) but I've also used the Muffle spell as a substitute.

My first character ended up in a full set of Daedric gear with Muffle enchant on the boots and Sneak at 100 plus I think I had the Muffled Movement perk, in a tomb or cave setting she could sneak right up to an enemy and never be caught. And I mean, close enough for a melee kill, standing basically right at the NPC's shoulder. That combo was also foolproof against Falmer, I don't think they ever got within melee distance of me after some point because I would one-shot them with a bow before they ever knew I was in the vicinity.

A (self-made) Muffle enchantment on your boots, or using the Muffle spell makes you move silently.
I have never got as far as the "Silence" perk before... (can someone confim if this is like the 'second' part of the muffle perk? I know that the muffle perk reduces noise by 50%... so does silence give the other 50%?)

I've done this for an archer, and have got a few backstabs too - though usually the eye icon was on the cusp of opening to full - I only just got those hits in before being seen!

-HK

It will be slow going until you get your sneak skill up.