While this doesn't directly answer your question, as I haven't yet heard rumors of a Dwarven "storehouse", I can tell you where to get a ridiculous number of Dwemer artifacts.
Nchuand'zel, the ruin beneath Markarth, is the richest I've yet found. To give you a sense of scale, I walked out of Avanchnzel with the materials to smelt ~100 Dwarven metal ingots. I have so far carried the materials for more than 700 ingots out of Nchuand'zel, and I'm not even sure I've gotten it all.
The spoils are split into two main areas — Calcelmo's Dwemer Museum, and Nchuand'zel itself. Both are accessible via Understone Keep in Markarth (you need to go through the Nchuand'zel Excavation Site to get to the city itself).
The ruin is populated primarily by Falmer, so is largely smash-and-grab. The museum is patrolled by guards who will attack you if you haven't obtained Calcelmo's permission and is a much sneakier affair.