PC upgrade or Laptop

I'd definately say that desktops are more reliable. Crucially, it's much easier to get drivers for desktop parts (many laptop users have to get unofficial drivers for Nvidia laptop cards).
What are you intending to use the system for?
When getting a case, don't bother getting one with an include PSU unless you know that the PSU is from a decent brand. Most generic cases come with generic PSUs that are pretty rubbish.

The Thermaltake is a good choice - solid PSU. You could always get a case you like and a separate PSU.
I'm not sure about the 8600GT. ATI cards are better for video playback, and the X1950's are good enough for the games you listed. You could always wait till later in this month when AMD release the R600 generation of cards. As you mainly use the computer for media, an AMD/ATI graphics card would be better suited to your needs.
Also, if you're not afraid to overclock, I'd recommend getting an Intel E4300 processor. The E4300 is cheap and overclocks easily.
Finally, how much do you use your DVD burner? If you use it as little as I do, you may as well carry your current one over and save a bit of $$ there.

I had quite a few problems with ATI cards ( driver problems and now something else with my 9550), this is why I thought Nvidia cards only. I won't overclock my CPU, cause I'll lose my warranty for it( and I'm not much an expert in overclocking), and I'm very satisfied with how my current CPU performed so I'll stick with AMD.
I'm from Romania, so I don't think that Newegg will ship it to Romania, if so it would take a lot of time, and money.
Peet

Then go with something in the 7XXX of nvidea, the 8600 just isn't worth it.

That's a better choice for your price range.

For portability, conveyance, room, and power intake a laptop is great, but only stable if you don't try to upgrade it, so you would be better off building the way you are going to use it until you replace the whole thing.

For upgradeability, price, performance, and overall stability under pressure a Desktop will work better.

It really depends on how you’re going to use your hardware and what for.

well...., it's a kinda sorta thing. Really your going to get more power for the price with a desktop, and you will be able to play newer games in two years without worrying about weather or not your computer can handle it, but with the games your playing you may not have that problem, if you get a higher end laptop, but you will be paying a good price for it. It really depends on if you ever want to get a really high-end game in a few years.

Just one more question. The 550w thermaltake PSU will be enough for the system I listed?

everything besides the VGA sounds good i wouldnt go under a GF 8600GTS ifi were you

well its ok it will be equal to a GF6800 in DX9 so i dont even know what it will be in Dx10