Question : Problem: CPU Case/Chassis

I HAVE SEEN SOME computer chassis & I am confused that whether the supplied power supply will be enough for my system. I don't want to spend more than $170. The two main problems I am facing is that I can get Case with PSU for as cheap as $40 & surprisingly with 550 watts. And the expensive ones come with less watts PSU. This is confusing.
For e.g.
Antec  NSK6580            480 WATTS ($135)
Thermaltake Bach VX    400 WATTS ($166)
SHAW Xtreme-550         550 WATTS($40)

So, should I buy Shaw Xtreeme beceause it come with 550 watts PSU or Antec NSK 6580 because it is better quality?

The Configurtion is:
AMD X2 5600+
ASUS M3A
ASUS PCIe 9600GT
4GB RAM
320GB SATA HDD, 160GB SATA
20X DVD BURNER

Answer : Problem: CPU Case/Chassis

I always recommend using a good quality PSU ... poor power can cause an amazing number of spurious (and hard to isolate) issues.   Look for a unit with active PFC (power factor correction) and reasonably high efficiency (> 80% is excellent).

The Antec case you suggested comes with the Antec Earthwatts 430w PSU ... which has both active PFC and is 80+ certified (means it is > 80% efficient at three different power ranges).

The Thermaltake Bach VX case is often sold without a psu [e.g. http://www.newegg.com/Product/Product.aspx?Item=N82E16811133043 ], so I'm not sure what PSU is included in the price you've listed.     Personally, I prefer to buy cases without PSU's, and I then always use either Seasonic or PC Power & Cooling PSU's [Both are excellent, top-quality units => but would like break your budget here => although you could come close with this unit:  http://www.newegg.com/Product/Product.aspx?Item=N82E16817151040 ]   (I know you can't buy from the Newegg links ... but they provide a good overview of the products)

I can't find any details on the PSU included with the Shaw case ... but clearly it's not likely to be a very efficient unit; nor is it likely to have active PFC.

Personally, I'd be reluctant to use the Shaw PSU ... especially with the quality of the overall system you're building (particularly the graphics card).   On the other hand, for the price, if you like the case, you could buy the combo and give it a try => and if you encounter any issues simply replace the power supply with a better unit (e.g. Seasonic).