Newegg has CORSAIR RM850X 850W Power Supply for 79.99 after coupon and mail-in-rebate. Cheaper than FP deal for similarly specced EVGA SuperNova 850W G2 (same cost as GQ model, but GQ isn't fully modular), although requires MIR.
Use coupon code UVXCE10
to take $10 off.
Review from JonnyGuru rates the RMx series as 10/10 (for RM1000X) and 9.8 (for RM750X).
The review isn't for RM850X model, but I suspect the build should be somewhat similar to RM750X, and considering both 750W and 1000W model earned over 9.0 score, I would say RM850X should also be pretty good.