Please help me calculate power requirement

I'm trying to figure out how many amps at 12v the system I'm building will require, since it seems like the true limit of basically any PSU is the amount of power is supplies on 12v rails. I have a PSU that supplies 17A at 12v and I'm hoping that will be enough. The system is pretty basic:

ASUS M3N78-EM mobo with NVIDIA GeForce 8300 onboard video
AMD Athlon 64 X2 5400+ Brisbane 2.8GHz 65W processor
1 SATA HD
1 SATA DVD-ROM drive
May add one or two IDE or SATA HDs and a TV tuner card down the road

I'm having trouble finding data on how much these devices will draw from the 12v specifically. The CPU isn't hard, since it draws all its power at 12v: 65W/12v = 5.4A. Let's say 6.5A with imperfect efficiency, though I have no idea at what efficiency I should expect the CPU to operate. But what about the rest? In particular, I expect the onboard video to draw significant power at 12v, but I can't find how much.

Can anyone help? And can anyone suggest a resource for finding this kind of information in the future? When I find power usage information at all, it's usually simply listed in watts, without specifying which rail it's drawn from.

I did find the following two links in thread:

http://www.extreme.outervision.com/PSUEngine
http://web.aanet.com.au/SnooP/psucalc.php

Both seem pretty useful (if a little out of date), but neither site seems to have good information on onboard video.

 

This little beauty will give you a bit more information...

http://download.cnet.com/HWM-BlackBox/3000-2086_4-10898732.html?part=dl-6312228&subj=dl&tag=button

 

This can help.

http://educations.newegg.com/tool/psucalc/index.html

or this is my favorite.

http://www.antec.outervision.com/