DSL is generally limited to around 3 megabits/second. Maybe they have juiced it up a little, but I would be surprised if it can do more than 5 megabits/second.
Unless Century Link DSL is just their brand name, and they offer fiber or cable to the home, or have a deal to carry the signal across the Cox cables.
I my current home, before we moved in, I paid about 2K to have Ethernet run to all the rooms (AND a 2 lines with an electrical outlet in key closets). That way I had Ethernet available everywhere. The closets are were I would setup routers or WiFi access points using Ethernet as the back-haul, or a network attached printer and the 2nd ethernet feed could be put into service as a FAX telephone line.
The house before that I ran my own ethernet from an electrical outlet on the first floor into the basement (drills were involved), across the basement, up into a hall closet that was under a 2nd floor hall closet, and through the upstairs hall closet wall into a bedroom closet (more drills were involved). That gave me ethernet in the upstairs office, and a place to put a WiFi access point, again using ethernet as the back-haul.
In your case, you if you cannot figure out the correct WiFi booster, you might just look at a pair of PowerLine Ethernet adapters. Plug one into an outlet in the great room, and the 2nd in the office. Plug ethernet cable from router into the one, and an ethernet cable from the other into your Mac. PowerLine will give you way more than 150 megabits/second.
