Just checked your screen shots. the download speed is only 3% faster and have you noticed your uploading speed is slower. I think we can blame these differences on random error rather than using 2 ethernet connections - due to the tiny downloading speed gain and the uploading speed loss that simply shouldn't be there should it be the dual connection that's affecting it.
My results on speedtest.net varied wildly.
Also, just to prevent misleading the guy, celegorm ment 100KB, not 100MB.
Do this multiple times and I'm sure you'll not notice that huge a difference.
How a test between 100MB/s and a 200MB/s connections makes a difference on a 5MB connection to the internet is pretty weird in IMHO. A chain is only a strong as it's weakest link, as they say. In the same way as a Net connection is only as fast as it's slowest connection, in this case the one directly to the net. However, if your results are indeed different because of the dual ethernet connection it'd be interesting to look into.
If I were you juiceranch9, I'd not bother with the hassle unless you desperatly need a uber fast connection to another PC within your network, provided you kitted it out with a dual connection too. If it was that important however, what about setting up a 1GB/s network instead?