Plan on building a PC soon, and have some questions about pricing. if you feel you have information that could help, please feel free to post.

My budget would be $700-$800. Now, obviously I would love to spend less money... on the other hand, I want a computer that will be able to handle both modern/upcoming and recent games. Along with that, I also want one that will not need upgrading for a few years (if that's even an option with the budget I gave). Basically, what i'm asking is what would be the estimated price for the type of computer I described? Some games I would plan on playing are Skyrim, BO2, BF3, GTA5 (I haven't seen the requirements for this game yet so i'm not too sure about that one as of now), TF2, L4D2, and games that will be coming out in 2013/2014. With that being said, i'm not looking to play the more advanced games (BF3, BO2) with maxed setting. In fact, High settings with 1280x720/1920x1080 would be more than good enough for me. Heck, I'd even be willing to go to Medium for the games coming out in the future (although it wouldn't be my first option). I don't want to make it sound like I want a casual computer, because I don't. I want a moderate/serious gaming rig.

So all i'm asking for is how much the estimated price would be. I don't need to know the parts yet. But if you want to post some links to give me more info, please don't hesitate.

Thanks in advance.