Thanks for the replies.
I am using the same overclocking app (setfsb) on both cards.
I have the 755 Desktop model
It has one PCIe slot rated (printed right next to the slot) as a 25 watt limit.
My new DELL ATI Radeon HD 4550 is rated the same 25 watts. The previous display card Nvidia GeForce 6800 is old enough that I'm having trouble finding a spec sheet online, but it worked with no issues other than being slow. But it was still 2 or 3 times faster than the imbedded graphic controller. The new DELL ATI Radeon HD 4550 is magnitudes faster than the GeForce 6800. Neither card requires a separate power connection.
Oh, I forgot to mention that I have an external 400 watt Power Supply, meaning I bought a PS harness that extended the length of the 400 Watt PS's cables enough for me to place the PS on the desk outside the rear of the computer. It performs just fine. Probably more than I need, but the 260 watt Power Supply that comes with this computer worried me so much, I just went ahead and installed the 400 Watt PS. I installed a large case fan where the power supply used to be to retain any air flow that the PS's fan might have provided.
I think that's it.
Eric