Do you have any wireless clients which will work with 5GHz band? If not, it is not nessary to buy a dual band router as your ISP speed is 4mbps.
How did you confirm that Wi-Fi problem is caused by old router itself?

After constant outages over several days, I did some troubleshooting. I connected my laptop to the ISP modem via an ethernet cable and did a speed test, which showed full speed at that time. I then reconnected the router to the modem and did a speed test via ethernet cable connection and it was less than half the modem speed. When I connected via wifi, I was at 0.18 mps. I reconnected directly to the modem and was again at full speed. This said to me that the problem was in the router. I should say that I reset the router to factory settings, reinstalled the Firmware updates, and reconfigured the router. I did the same testing as before with roughly the same results. This said to me that the router was the issue.

I see...
Do you still want to buy a dual band router like C7 or just a single band router like TL-WR841ND? :)

Given that the infrastructure of our country is ever improving and that hopefully soon we will be connected to the fiber optic network of our nearest city, I will still go with the C7. It is uncertain when we will be travelling back to the U.S. and the costs of such purchases are prohibitive here, so I will purchase for the future connectivity.