Help with power requirements for an ATI 4670 inside of a Dell

I'm trying to put either an ATI Radeon 4670 or 4650 inside of a Dimension E521 desktop.


I noticed the huge gap in frames per second between these 2 cards, with the only major difference being the power consumption, but the prices of these cards are relatively similar.

My questions are, what are the power requirements for these cards? What does a 12V rail mean? (I'm guessing this is the line in which the card is powered which is a 4 pin) Also, how can I tell by looking at my psu specifications that my power supply has enough volts on the 12V rail to power one of these graphics cards?

Now I understand that the recommended power supply requirements for these cards is 400w, but I feel that's a bit overabundant, specifically for the 4650, as I've read that people have ran this card with 250w power supplies.

Here's the power supply that's inside the Dell I'm trying to upgrade:

Model: H305N-00 (I'm not sure what the form factor is)

Max power output: 305w

AC input 50-60 hz

DC output +5v - / 22A, +3.3v / 17A
+ 12va / 18A, + 12vb / 18A
-12v 1A, +5vfp / 2A

Can someone please explain to me what I'm looking at here and what's relevant for when upgrading graphics cards?

I'm trying to keep my budget under $100USD. So if I end up having to buy a new power supply I'd prefer it to be a cheap one. Also, if I end up getting the 4670, should I get the one with the fan or the huge heat sink?

Input is greatly appreciated!

Here's a graph that shows the actual power requirements of different graphic cards.
http://forums.atomicmpc.com.au/index.php?showtopic=264
4670 = 47w at load.

The Dell E521-S is the slimline system. Your power supply is just fine for the HD4670 and the 4670 does not require any additional power from your PSU.

Here's 3- 4670s that would be good choices $70 - $80 not counting rebates. A Sapphire 4670 that is only a single slot card, it'll be easier to place in your system and less chance of it blocking a SATA or other port. May be a bit louder and warmer then a dual slot card.
http://www.newegg.com/Product/Prod [...] 6814102820

Another Sapphire card, this is dual slot, but uses DDR4 memory, it's a bit faster then the DDR3 card.
http://www.newegg.com/Product/Prod [...] 6814102818

HIS IceQ - dual slot has the best cooling of the 3 cards, exhausts hot air out the back of the case.
http://www.newegg.com/Product/Prod [...] 6814161252

I have a E521 system and I got a 4650 heavily OCed. You should be fine with either.

Ok, I didn't type it completely.. here it is:
+12V/18A, -12V/.8A
+5V/22A, +5V/2A
+3.3V/17A

I have the 530 mini-tower.. so I guess I'll just get the plain vanilla 4670. Thanks!