You can see it in the Bag Settings. You can choose which items you want to pick up into which bag and there are options like "Epic and above" which shows Epic in a purple colour.
I'm still working on this quest, so I'm not the best authority, but I upgraded my Armor shop to the max and by restocking it several times, I've built up three out of six items (Shiftsteel). I have a feeling I'm going to have to grind for a while to get another three.
I'd like to know why this is a Medium quest; I completed all the other quests, including the Hard ones, some time ago.
You know it's much cheaper to accrue a lot of money on your main characters, quit, start a new game with a level one character, go to the store, restock to your hearts content until you find the armor you are looking for.
Gantic -- Thanks for the tip on using Level 1 characters to restock. As it was, I started with $40,000 and after restocking and trying to figure out which ones of the ten sets would "win," I finally got #6 with $6,000 to spare. (I ended up with the Aetherweave set, which looks kind of cool.)
I guess my suggestion after this experience would be to just grind the stocking aiming for one set. Trying to fill up three or four sets at the same time was complicated and time-consuming, and expensive.
You don't reset the game data. You just choose a level 1 character or your lowest level character and start a new campaign. Instead of fighting monsters in that campaign, you just go straight to the shop and restock the armor until you buy all the pieces of one epic set.