If your power supply is old or crappy, then there is no better card than the ATI 4670. It has no external power connector so it's  friendly with low wattage power supplies. I personally wouldn't bother with the other two you mentioned as the 4670 should only cost about $10 more than the 4650 and any card lower than that probably wouldn't be enough of an upgrade to bother with. If you told us anything about your power supply or what your budget is, we could be much more helpful.

Hey Zelda, I would recommend a 4850. You can get it from sites like newegg and tiger direct for pretty cheap.

http://www.newegg.ca/Product/Product.aspx?Item=N82E16814121272

Here is an example of a 4850 at $155 with $30 mail in rebate on top of that.

If you are willing to spend more try this 4870

http://www.newegg.ca/Product/Product.aspx?Item=N82E16814102810

It is $183.49 with a $15 mail in rebate on top of that.

In general I would recommend upgrading to an ATI card on a computer that previously had an ATI card because of possible residual driver issues.

i got my 4670 off newegg for $90, you should try there.

my psu is only 300 watts and it works great- better than my friends 9600 which requires pins. I also have a quad core and more than one HDD in here

if the PSU is 5 yrs old it NEEDS to be replaced!!!!!!!!!!!!!!!  best advice is to replace every 2-3 yrs, after that you enter the aging danger zone.

power supplies lose output ability over time, upto 30% in an average of 3 yrs. meaning a 500W 3-5yr later may only be a 350W supply. and likewise for the AMP output. if it was a 40A it may now only be 28A.

there are certain variables to this including but not limited to, quality of the PSU and how much the PSU is run at peak power.

no. please go do some research on PSUs and how they operate before you give advice.  

the power rating has nothing to do with x capacity due to heat. a 500w PSU will put out 500W however most power supply companies rate the PSU wattage at PEAK power which is the max amount of power it will put out. some companies like PC Power & Cooling rate PSU at CONTINUOUS power (the amount of power used in normal operation) you will hit peak power depending on the system config and what you are doing such as extreme gaming or other graphics work.

 your thinking about the efficieny rating, if a PSU is rated 80% efficient it merely means that 80% of the power coming into the PSU from the wall will be coverted to watts and then amps for power out put. the remaining 20% is lost to heat in the process. It has NOTHING to do with the wattage rating of the PSU. another factor of the efficiency rating is the temp it is rated at. a PSU rated 80% efficient at 25C is garbage because your PSU will be above 25C 10 seconds after power on. what you want to look for is an efficiency rating that was taken at 40-50C which is the average operating temp of a PSU.

the efficiency of a PSU can come in to play for the life of the PSU and how soon it loses output ability, as well the size of the PSU can play also. if you have a low efficiency PSU it will run hotter, likewise running a PSU that is just barely large enough for your system can hurt in the long run. yes it will run the system now, BUT, if you do a lot of extreme stuff and run that PSU at PEAK or close to peak power a lot it will run hotter.

all that heat will speed up the pace at which the PSU loses output ability.

the best advice is to run a PSU a little larger than you need. such as if  you NEED 500W 35A, run something like 650W 40A+, this will allow you to stay out of peak power more and keep heat down. which in turn will slow the rate that the PSU dies (loses power output)

the PSU is the most important component. run one too small or too old and you WILL eventually fry components due to lack of power.

Good advice Blackcurtain.

Best to always upgrade GPU witha new PSU. Those cards only do what they say they will if the power is there to do it.

that would depend on the size and age of your power supply.

ATi recommends MINIMUM 400w supply for a single 4600 series card, and 550w for Crossfire. I could not find exact specs on a quick search but this leads me to believe that the card can use in the area of 100w, possibly ~150w at peak operation. which amounts to  8-12.5 amps, which is the more important factor to look at. it is the amps that power the system but you have to have the watts to get the amps.

1. it is not recommended to go with MINIMUM, I always go larger because it also depends on what else is in your system for power demands.

2. read my above post.

For the record, I think we can all agree that you're about due a new PSU before you upgrade to a brand new expensive graphics card.

Am using a 4650 in this after using a 9700GTX for quite a few years. It seems to run cooler/faster than my old Nvidia card and it defo uses less power. Am a happy bunny with it as I can now see where UB has left his little puddles now. Runs fine on my 500Watt PSU

only JUNK PSUs are rated at room temperature!!! Room temp (depending on variables) is about 70 - 80* fahrenheit (ie 21C - 26C) yes some PSU manfacs rate PSUs output and efficiency at 25C.

the problem with that is your PSU is WILL be 25C hours after total shut down, the PSU will exceed that temp within 5-10 seconds of operation, at which point efficiently, power output  and quality are shot out the gate.

a PSU operates at 40-50C (104 - 122 Fahrenheit) way above any average room temp unless you live in the hottest deserts. ONLY PSUs rated to operate at these temps can be anywhere close to quality PSUs.

an operation rating temp of 40-50C should be the first thing one looks at when buying a PSU, that way you can eliminate the obvious junk before even looking at watts and amp output.

yes, good quality PSU power output is rated at continuous, problem is only a VERY FEW do this, most PSUs are rated at peak output with continuous output being 50-100W less depending on the manufac and the size of the PSU. even the manufacs that most people rave about being the best, such as Antec, Enermax, etc.... are rated at PEAK power. ANTEC and possibly few others are realizing and beginning to change and rate some PSU lines at peak power, but the vast majority of their PSUs are still rated at continuous.