Clodydild

I have already used that.

Looking at the specs on that board you should be getting 3.0 x16, not 1.1, but unfortunately I don't know why you aren't. My hardware is pretty old but both of my GTX670s show 2.0.

The only real upgrade is the GPU. You'll be capable of playing comfortably in 1440p if you would like to in the near future, and you'll definitely gain FPS in your games, but it's not really worth it. An upgrade like that is not worth the money if you are playing your games at the settings and FPS you would like. If you do end up upgrading, you might want to swap out the parts yourself. Just an idea, though, you've got time anyways.
However, if you really feel the need to upgrade, you should probably wait until Nvidia releases their new GPUs and AMD releases their new processors, just to see what is better or worse.

ArmA's pretty fun, has a shit ton of mods (DayZ being one of them), and also has a lot of graphics settings so you can play it fine on netbooks even. Its a combat simulator, like Battlefield but much more realistic. However, its meant for online play (but does have single player campaign). You should also give Saints Row a go, which again, has plenty of graphics settings.

Papers, Please is a fun little indie game. There's also Payday 2 which is a nice FPS game that revolves around robbing banks and purchasing different weapons/skills to better equip your character. It's centered mostly around online gameplay but you can play alone or with the AI.
 
 

Yeah, Maszyna can be fairly similar and is my personal favorite of the above. They're always doing updates to it though, and eventually they do updates, like make certain systems behave more realistically, make locomotives behave and sound more realistic, even have things such as coupling done in a more realistic fashion. The graphics don't really kill it too much for me to be honest, and have still come a far way compared with the earliest versions from about 13 years ago. If you have a hard drive that can handle the rather small 1 Gig, and don't have a problem torrenting it (as this is how the current versions are now distributed), it is worth a look, even though there might be a small language barrier as most everything is in Polish. There is a really good site though to reference for meaning of the Signals and signs though.
 
That and I like how the signals seem to have their behavior realistically modeled. There is also another sim from way back then that is also of Polish origin, called Mechanik. It put you in control of a Class EN57, and was fairly decent considering it's age, but Maszyna far outdoes it now.

Of course, MSTS runs a very close 2nd in my book, especially as it allows me to replicate a good chunk of the Amtrak Floridian (Chicago-Louisville (Monon-2 route), Waycross-St. Pete (Florida (Folkston) Funnel and the SCL A line beta)), and with a way to get appropriate (or near appropriate) equipment to do it.

I thought of another good game one can get off of Steam. IL-2: 1946. It does have a large learning curve, especially if you're going to play online, but it is essentially the Gran Turismo of WWII Aviation (and some mod packs have it go further). Once you find yourself understanding how to actually hit something, the rest comes down to understanding your aircraft and any evasive manouvers (almost impossible in a bomber, but I find flying high and planning around the big combat areas where the fighter jocks are tearing each other apart tend to work best. And even then, there is some issue as some people have found a way to make a cheat radar to find you apparently, as was revieled on the UltraPack mod forum.) Have to say, Steam does have some neat sims, with learning curves ranging from highly watered down (TS2014) to hyper realsitic (DCS sims are a good example here.)

Problem with train simulator, it gets boring after a while, at least, that's my experience. With a game like prison architect, unexpected things are happening, you keep improving the prison, you have to respond to riots, fires, fights, breakouts, etc etc. 
But yeah, now you know multiple peoples perspectives about a few games. Have fun choosing which one I would go for prison architect =D. :p
 
 

I would go for prison architect, it is a great game with active developers who keep improving and updating the game in many ways. I have the game myself! Concerning your FPS, the game is not demanding. :]
 
Good luck!

This is pretty awesome! Would love to see it slightly tweaked to:
Be in the corner of the screen.It's a struggle to see the plate number when the computer's text is in front of it Be able to type with keyboard and drive with Xbox controllerSometimes the car moves slightly forward, and the plate becomes difficult to see Optional auto-complete featureManually typing it in is more realistic, but some plates are difficult to distinguish between 0's and O's. Would be great to have the option to auto-input the plate number

Starbound is an excellent game I had a blast playing that and even the slowest of computers can run it. 
 
If you enjoy games where everything is destructible and you can build your own worlds like Minecraft and Terraria you will enjoy this game heaps!
 
Plus I think it's only about 15 dollars on steam and you get tons of gameplay out of such a cheap game!
 
Just my 2 cents :)

Very good suggestions for train simulators mate, I've used all of which you listed, and if I have to choose, Microsoft Train Simulator is still the one I enjoy the most. I'm also playing "World of Subways Vol 3, London Underground" which is a solid train simulator, not a environment simulator. The game looks good, but the stations, tunnels etc are pretty bland. Still, I enjoy it. 

I'm guessing he's talking about GTA IV/LCPDFR.