Is it REALLY not possible to purchase a SIMPLE device to accomplish this?
I think you misunderstand the problem entirely.
Its not so much throwing "a box that works" at the problem, but rather you having to make the time and effort to understand the local factors that will greatly affect WiFi quality. Until you take the time to do that, no matter how much money you throw at a WiFi base station, you will likely continue to have disappoint results if you set it up wrong.
Google will doubtless throw up a suitable number of results for what needs to happen if you wish to do a DIY WiFi site survey.
Just one example of many of a local factor.... modern stud walls with foiled backs will have a very undesirable effect on your WiFi signal. Your choice of signal channel is another example, for example if you've got a bunch of neighbors on channel X and your kit is also configured for channel X its going to be one big digital bunfight !
But there are hundreds of possible local factors, far too many to even start listing here .... so either do your homework, or pay a reputable company to come do a survey.
Personally I am a great proponent of structured cabling where possible rather than jumping on the WiFi bandwagon. Speeds will always be greater over physical cable and reliability over physical cable will be a lot better for the majority of people. But I understand many people prefer wifi and so they just need to put the effort into a proper survey and implement the results correctly.