Hey Shawn,
So your Droid doesn't have any of those pauses that you experience on your desktop computer? Was the streaming issue on your computer or were you using a console?
If you have access to another computer, a friends laptop for instance, it can aid in troubleshooting the issue. First, make sure that the computer you're using is reliable and fast. Connect it the same way that the desktop is being connected and test it. It sounds like you've troubleshooted the rest of the equipment the right way... you eliminated extra variables like the router and swapped cables and your modem. It's most likely the adapter or something software related in the OS. Especially since the droid isn't showing the same pauses.
If you can't get your hands on another computer (or after you test on another computer and find improved connection) another thing you can do is buy a cheap (or a nice one if you think you might want to keep it) USB CAT-5 or wireless adapter (or PCI / PCIe... sounds like you're comfortable inside your computer). Make sure you buy it from a store that has a good return policy because you may or may not want to keep it afterwords, depending on the outcome. ... if you still have the same issue with a different adapter on the same computer then it may be something software related, again... trying another computer, hooked up the same way as your computer will prove that it's an isolated issue and not an issue with your provider, modem, router or cables.
... Let me put it this way... even if they cut your speeds... you shouldn't have pauses like that when you test. That's a major indication that there's a problem.