That's not where they advise to install that router. I suggest moving the router to a better location and 5GHz is nice to have but in my experience it has shorter range than the 2.4GHz.
I have a bit of a unique situation here. I have a fairly large 2-story house with a basement. My DIR-655 wireless router is in the basement, and it is the only wireless router plugged in. Using my Galaxy Tab 10.1, I can get a signal strength of 3-4 bars almost anywhere in the basement. The problem is, when I am the next floor up, and only around 10 feet away from the router relative to the floor, I can only get 2 bars or so. It gets even worse when basically directly above the router, but on the top floor, where I get 0 (Android shows this as very poor signal) to two (if I'm lucky) bars.
Would I benefit from getting a newer router with a better signal, and would 5GHz help? I CAN NOT use a second AP anywhere except the basement, there is no Ethernet running on the other floors. While I could move the router within the basement, I have already tried this, and it gets better in certain places as expected, but is still poor elsewhere. While I can pick up a few (poor) signals from neighbors across the street, i can barely get wireless on the top floor of my own house.