Gigabit connection with very slow download speeds

I recently subscribed to Uverse Internet with gigabit connectivity. Regardless of the time of day or the site I go to when I need to download files I typically get speeds in the 100s of Kbs. When I run the ATT speed test my DL throughput is always over 500 Mbs the last was 825 Mbs. When I had Cox I never encountered this problem with my 100Mbs connection so this is frustrating to say the least.  Sample sites in question are Microsoft, HP, Steam, Origin, World of Warships.  I am attaching a screen shot of my DL throughput from World of Warships this morning.  I connect my PC to the modem with a 6' Cat 6 cable. 

My PC Specs are as follows:

Intel Core i7-4790K @4.00GHz

16 GB RAM

Samsung EVO 1 TB SSD

1 Gb Intel Ethernet Connection 218-V

Windows 10 64 bit Home

My Modem specs are as follows:

Manufacturer Pace Plc
Model 5268AC
Serial Number 30161N012380
Hardware Version 260-2173300
Software Version 10.5.3.527171-att
Key Code 52HP-2374-2262-22AT-F2BQ
First Use Date October 28, 2016
Current Date Wednesday, November 30, 2016
Current Time 11:51:20 AM
Time Zone Central Standard Time
Time Since Last Boot 1 day 22:45:03
Device Access Code Default Access Code
System Software Components
Type
Version
att_unified_eapol-certs
527171
att_unified_config
527171
att_unified_cms-certs
527171
Firewall Rules
1000
Application List
1001