Will Shock Blast reduce the cost first or will Researcher is Empowered trigger ability reduce the cost first?

You choose the order — discounts are applied by you in any order (Rule 356.4.d), but to get the lowest cost you should apply Applied Researchers' discount first, then Shock Blast's.

Here's why the order matters: Applied Researchers' −1 has "to a minimum of [1]," and that minimum only constrains its own discount (Rule 356.4.e). If you apply Shock Blast's −2 first, Researchers' −1 can only take the cost down to 1. If you apply Researchers first (e.g., 3 → 2), then Shock Blast's −2 applies after, dropping the cost to 0.

So the practical answer: Researcher first, Shock Blast second, and the total is your printed cost minus 3 (with Researchers also removing 1 [A] from the Power side, if any), to a minimum of 0. One note: "Shock Blast" isn't in the card database, so this assumes the −2 reduction you quoted — same math applies if the printed cost differs. (FAQ #11897)