replacement HDD's -power and other considerations

Will installing newer, faster HDD's on older desktop systems put additional strain on power supply?

I am looking to purchase replacement Hard drives for windows workstations.  Most of the computers are Dell Optiplex 320's with older SATA connectors (3gb/s) and 400 watt power supplies.
The existing drives are 250GB/SATA 3.0/8MB Cache/5400rmp.
Will there be any issues replacing failing hard drives with newer WD hard drive that has 7400 RPM, larger 64mb cache?
I don't have the exact specifications power specifications of each part.  I would prefer to replace the drives with a model that is similar in power consumption, so it would not put too much additional strain on the power supply.   Ideally the new drives will be of better quality (faster, larger).
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Scott CSenior EngineerCommented:
400W power supply will be more than enough for when you replace your drives.

You would only need to worry about larger power supplies if you were adding in more HDDs and high end graphics cards, and may more devices.

The new drives will consume so little amount of extra power it isn't worth worrying about.

You will be fine.

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AE_JBAuthor Commented:
Thanks.  I wanted to throw this out there to make sure I am not overlooking something.
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