So I had asked the question regarding if the G74SX will handle more than 1.5TB as stated by ASUS, but no one seemed to know... Took the plunge and bought a HGST 1TB 7200RPM drive... To my surprise, windows saw the full drive (932GB)... So what I gathered is that the 2 main SATA 6GB ports are limited to 1.5TB probably (not something I will bother to test since SSD's are in one of those SATA 6GB ports)....
Currently: SATA 6GB port 1: INTEL 180GB SSD SATA 6GB port 2: Seagate 750GB HDD SATA 3GB port 3 (Optical Bay) : HGST 1TB (will be moved to a 6GB port, even though I am getting 140mb/s read/write speeds on the 3GB port)
GL702VSK / GTX 1070 / M.2 960 EVO
HTPC MINI-ITX / FRACTAL CORE 500 / GIGABYTE GA-AB350N / GTX 1050 Ti Windforce OC 4G / RYZEN 5 1600 3.9GHz / M.2 960 EVO / G.SKILL Ripjaws V Series 3200MHz OLD ASUS G74SX-XC1 / INTEL 7260 AC / Samsung 850 PRO / TUNIQ TX-4 / BIOS 203 / 335.23