Hi all, complete noob to networking, but been a PC builder for a long time. I'm a RF/Wireless EE in the infrastructure tx / rx signal chain, so I'm pretty good at following directions. Every time I've undertaken a networking upgrade however, it's never gone very well, as it just vexes me. 
My goal: better wi-fi coverage of my house
My "setup": My standard Verizon FIoS Actiontec router sits in the "basement" level of my house, in the back left corner floor level, as you are facing the front of the house. It's the sole wi-fi signal for our home. The living room, is on the "1st floor" one level up, and on the complete opposite side of the house (typical sized home, 2k sq ft). Our bedroom is directly above the living on the "2nd floor".
I have small WHS2011 PC we use as a NAS that is hard wired into the Actiontec, as is another PC, and a WD HD Live TV Plus box for the family room (on the "basement" level). The last LAN port on the Actiontec is to a TP Link Ethernet over Powerline Adapter, that has "mates" in the living room, our bedroom, and another room on the "1st floor" (all mated to WD HD TV Live Plus boxes / TV's for video streaming). Running new cables isn't an option, sadly.
"A guy at work" said that the first thing I should do is call Verizon and have them ship me a new router, as I have a first-gen one (when they first pushed FIoS through our neighborhood 7-8 years ago) and get the newest version, and then buy an Asus AC66U. I'm to turn off the wi-fi on the Actiontec, use it as just a router, then plug the AC66U into the TP Link box in the living room, and have the wi-fi there, and plug the WD box in the living room, into the Asus, thereby switching the floor and side of the house that the wi-fi signal is on, covering the living room / bedroom much better than where it sits now.
Is this how I should go about it? Is there a better way?
I should say our wi-fi load consists of mainly iPad's, Android tablets, a couple laptops, and several phones.
Any thoughts are appreciated, TIA.

My goal: better wi-fi coverage of my house
My "setup": My standard Verizon FIoS Actiontec router sits in the "basement" level of my house, in the back left corner floor level, as you are facing the front of the house. It's the sole wi-fi signal for our home. The living room, is on the "1st floor" one level up, and on the complete opposite side of the house (typical sized home, 2k sq ft). Our bedroom is directly above the living on the "2nd floor".
I have small WHS2011 PC we use as a NAS that is hard wired into the Actiontec, as is another PC, and a WD HD Live TV Plus box for the family room (on the "basement" level). The last LAN port on the Actiontec is to a TP Link Ethernet over Powerline Adapter, that has "mates" in the living room, our bedroom, and another room on the "1st floor" (all mated to WD HD TV Live Plus boxes / TV's for video streaming). Running new cables isn't an option, sadly.
"A guy at work" said that the first thing I should do is call Verizon and have them ship me a new router, as I have a first-gen one (when they first pushed FIoS through our neighborhood 7-8 years ago) and get the newest version, and then buy an Asus AC66U. I'm to turn off the wi-fi on the Actiontec, use it as just a router, then plug the AC66U into the TP Link box in the living room, and have the wi-fi there, and plug the WD box in the living room, into the Asus, thereby switching the floor and side of the house that the wi-fi signal is on, covering the living room / bedroom much better than where it sits now.
Is this how I should go about it? Is there a better way?
I should say our wi-fi load consists of mainly iPad's, Android tablets, a couple laptops, and several phones.
Any thoughts are appreciated, TIA.