I use a dual monitor on a Radeon X1650 so the X1550 should work as well

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Two notes of caution - use ATI's latest Catalyst drivers when you install and follow the installation instructions to the letter. I've found that it can be a real pain to uninstall and reinstall Catalyst.
I also found that the X1650 needs to pull a lot of juice on pc start up. So much so that I ended up having to pause it at boot up for a few seconds to allow other cards to start. That's despite using an 800W psu.
Anyway once installed and running it's a pretty good card in my experience. I can't use a pci-express so I'm limited for choice but the Radeon works fine.
Best,
Tony