Hi everyone - its my first time here so be gentle with me!
 
I'm building my first ever PC and  was wondering if the 500watt PSU in the Sonata would provide enough power for the following:
 
Q6600 with a Zalman CPNS9700 (eventually overclocked)
Gigabyte P35 3DSR
Sapphire HD4850
2 x Western Digital 500gb (WD5000AACS)  
Corsair 2GB Kit (2x1GB) DDR2 800MHz/PC2-6400 XMS2 Memory Non-ECC Unbuffered
Philips DVDRW
 
I can't see me every going Crossfire/SLI.  
 
Any help would be gratefully appreciated.  
 
M.

The Earth Watts PSU that comes with that case is good and yes it would run that system.

Just concurring.
 
That would definitely be fine.

I've that same PSU running a 2160 OC'ed to over 3.0 GHz, 2 GB RAM, Asus wifi P35 mobo, 8600 GT OC, 2 HDs, and 2 optical drives and it's got room to spare.  You should be more than fine.

You should be fine, just remember the farther you push your cpu and video the more power they take.  
 
It is not linear either, so a Q6600 @ 3.0 generally only takes 20-30 watts more, yet to add another 600MHZ you need 50+ watts at 1.4 and 86 watts more @ 1.5 volts(here you are talking over 200 watts for the cpu alone).  
 
There is a point where the extra speed is just not worth the extra power. The same goes for video, at one point the power increase per MHZ starts to get up there.
 
As long as your clocks are not out of control(trying to turn that 4850 into a 4870 and Q6600 @ 3.6+) you have plenty of headroom.