It isn't a derailment, what screen you're going to use, where will you sit, can you kb and mouse etc. are all considerations to gaming on a pc.
I think for me and maybe you fall in this too, I can't see me leaving consoles any time soon. They're what I grew up with and enjoy. However, I do like having a PC for the things a console can't do - like a proper racing sim, modded minecraft server, gmod etc. None of which really require the pin point accuracy of a mouse so you may be able to get away with a controller.
I feel like I am being quite negative about you getting a pc and I don't mean to be. I just don't want you to spend a few hundred quid (or however much) with the idea of playing R6 or OW etc only to find that you can't compete.