I'd recommend picking up a high-end machine, installing Linux (CentOS is what I use), run apache, php, mysql, etc (whatever you need configured), and then throw it on a good connection. Note, you arn't going to be able to run a decent server on any OS other than Linux, it's the best. Also, make sure you're using a good connection - if you have a high traffic site, the average broadband connection isn't going to be able to handle the upstream
I agree 100% with Syndication. For ex. my upload speeds are like 100KB/s not nearly enough if you want a good server.