Is the power supply enough?

this is the computer i have

http://www.bestbuy.com/site/olspage.jsp?skuId=9081325%26amp;type=product%26amp;id=1218017465909

i wanted to change the video card to a ati radeon 4870 x2 add a blu ray drive, a physics accelerator card, a better xfi extreme gamer sound card.

Is the 500w power supply enough if not how much power i needIs the power supply enough?
PhysX? Nvidia cards have it built in, but it sucks anyway. Forgoe that old card unless you get one really cheap (%26lt;$30!)

Also, for one 4870x2 on a Nehalem system, I'd suggest a top-quality 600 watt, and for two, 850-1000w. If you want the very best, get an Antec Signature 850. Also, hope you have some plans to add serious cooling to that box!Is the power supply enough?
ATI Radeon鈩?HD 4870 X2 System Power Requirements:

650 Watt or greater power supply with one 2x3-pin PCIe庐 power connector and one 2x4-pin PCIe庐 power connector is required



Certified power supplies are recommended. Refer to http://ati.amd.com/certifiedPSU for a list of Certified products



1K Watt with two 2x3-pin and two 2x4-pin connectors for ATI CrossFireX鈩?technology in dual mode