VLC doesn't cache to the hard drive like DIVX it plays direct from the host.
VLC has a really small cache size 5 seconds if you followed the tutorial.
Your speed doesn't determine how fast you download from a host.
The hosts will determine how fast they let you download (sever load,your location from the sever,ECT) if they are slow you will have the buffer problem.
If you have this problem and insist on using VLC then the simplest thing is to just download the file, and watch after it is finished or watch the .part file after it has had a few minutes head start.
Then delete the file after your done with it.
If you use divx it does cache to disk so you can pause it and let it get a head start before watching.
The other thing is to get premium from the host to increase your download speed from them. Which 180 and Billion doesn't even offer.