I configure a wide variety of serial devices such as network switches and routers in the field. When I moved to my first usb-only laptop several years ago, I had to find a usb to serial solution. Like you, I tried several USB to Serial adapters from the local stores without any luck. I As a last ditch effort, I ordered a Keyspan adapter online based on a past experience with them and it worked like a charm. I even ordered a spare after several months of use because I was afraid it'd be hard to find a replacement later on.
It has worked flawlessly while communicating with serial hardware (both new and old) on Linux, OSX, and XP over the past few years. I assume it'd work fine with later versions of Windows too. I doubt the power issue will be a problem with this adapter. Give this a try if the PCIe card doesn't work out!
Make: Keyspan
Model: USA-19HS
Keyspan High Speed USB Serial Adapter Serial adapter - USB
http://www.google.com/products/catalog?q=usa-19hs&cid=14565954588677202805
HTH, Jason
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Jason Klein
Datility Networks, Inc.
Internet Hosting / Network Consulting
v 316 282 0774 f 316 263 4829
e jkl...@datility.net