The only thing I haven't done is a VPN. I'll download one and give that a try. It's frustrating though as I have never had this issue before and still have the same ISP as always. I also have 1gbps speed and this is the only thing I've ever faced this slow download issue with. I'll report back to see if the vpn helps.
Update: The VPN did the trick. Guess I'll keep that around for when it's time to update GSX!