$2000 to $5000? that's obnoxiously expensive. Even if you wanted to build something that could play everything to absolute maximum at the highest framerates and extremely high resolution it wouldn't cost that much. Liquid cooling is very extreme. A lot of people try talking others into doing it because they're really into tweaking their computers and seeing varying increases in performance. But ultimately, if you, personally, don't care ... don't let anyone talk you into something like that.
If you want to get into enthusiast PC gaming, then I'd suggest a build like this:
$1556.76 for this Intel and Nvidia machine. It's a i7 5820K CPU (which is the lowest in Haswell E chips, the highest is about $1K) It can utilize 12 threads at once across six cores. So, it's going to have long legs.
The 770 is going to run everything pretty awesome. The power supply has enough headroom to support a second 770.
The RAM is pretty top of the line, but only $20 or so more than what's commonly used now (and is significantly faster)
The board is pretty spendy, but it's required due to the new CPU, as is a custom cooler that is compatible, those both add quite a bit to the already somewhat expensive CPU.
If someone is going to charge you $1500 or more ... If I were you I wouldn't accept anything below this build. You're otherwise being ripped off. For an enthusiast build, this is a pretty sweet setup. (Also consider for less than $2K, you could put in a second 770 into this machine, it'd be like $1860 or something, and it'd chew anything up completely maxed as several resolutions)
Here's a couple other options:
Intel Build:
Runs at about $1015. The only way to lower the price without sacrificing the graphics ability (which is the most important aspect for games), you'd have to start looking at AMD, because at similar prices, the Intel chips just don't perform as well. Getting an i3 instead of a FX 8350 doesn't make a lot of sense.
You can lower the cost if you're OK with giving up Nvidia. AMD GPUs are a bit cheaper, and perform a bit better in most benchmarks. It would get the build below $1000.
AMD Build:
This comes up at $905, you could get it sub $900 with an AMD GPU. With that and an FX-8320, you could get it down to $850 or so.
The power supply has enough headroom to SLI the card ... and this board support SLI and Crossfire fully. So, you can choose which ever you want.
This is going to play games virtually identically to the above system ... and you can actually shave the parts some more and push the price down still.
They're going to perform pretty much the same.
If you're aiming at a hard $600, but you want to be able to actually play games at 1080P, this is what I'd suggest:
Budget Build:
Comes in at $652, is going to perform in games within 5 fps of the previous builds. It has a little less headroom for upgrading (though you can later put in an FX 8350 in it and faster RAM)
It's not sacrificing graphics performance at all. It's going to run everything well above medium settings at 1080P. And is easily the highest performance per dollar you're going to get. This is the only build I've listed that isn't using a white case, because, for quality, you can get black cheaper. The minimum quality white case I found was $100, which is almost $30 more. That would push the entire build up to $682.
You can cut the price down more if you get a R9 270. But it'd still be above $600. There's a bit of a hit to performance too, and it performs better than a GTX 750.
In terms of enthusiast building, there's a lot of options. The initial build I put up is a beast. But you can also build some things in the same price range that solve other problems. If you built a Mini ITX box, for instance, you'd have something about as powerful as the mid-range builds I listed here, in the size of a small VCR form factor. But it comes at a price. It's about $1300 to do it.
You just gotta weigh what you want. What do you want this thing to do? How much are you willing to pay? How long does it need to last without further investment? etc.
Laptops:
