If you are programming for the web , as i am sure you know, the computing requirements are more of a none issue. Assuming you only need to work, I would recommend going simple. Get a notebook with a decent size screen (whatever your comfort is, I prefer 13 inches). I would suggest probably an i5 processor with 8gb of memory. Go for build quality over specs value.
I like Asus myself
Any modern desktop will be fine. As will any configuration of monitors. Personally, I do all of my programming on my 13 inch ultra book. I use multiple desktops in linux instead of multiple montiors. At home I have three cheap 1080p TN panels that work well enough, mounted to the wall with 20 dollar mounting brackets.
For web programming I don't know of too many good IDEs. There are lots of guys making the web like yourself, who don't come from a university or professional background. If you have gotten this far without an IDE, I don't see the need to adopt one now.
Personally I am doing a lot of programming in the MEAN stack. My setup is really simple. I have nodemon running through the terminal, which automatically refreshes my server ever time I make a change. I use sublime text editor with a Jade package, which gives me some simple text highlighting when I am programming my HTML. I use git through the terminal for version control, and I collaborate with my team through github.
When I am programming on my personal website I use a simple FTP client, a web browser (chrome has some pretty nice dev tools) and my favorite text editor. I use notepad++ a lot when I am working on large files, and it has some pretty nice features. If you are comfortable with that I recommend sticking with it. You should know, for what it is worth, all the 'cool kids' are using sublime right now, so if you are feeling adventurous, I would go ahead and give it a shot. Compared to notepad++ they are pretty similar, with sublime having a bit more bling and some more robust features for hotkeys, file viewing, and auto filling.