With our german hattrick online radio, we are using
http://www.server4you.net/
They have servers which seem to be big enough for 45 Euro (or 55 if you want Windows OS)
But they also have virtualServers here:
http://www.server4you.net/vserver/
Don't know about their performance. I guess, if we pay for an expensive server then we'd definitely need to play pitboss that way (or use a cheaper as I guess the forum doesn't need a fancy server, just enough space and traffic)
I heard people talking well about
:
http://www.manitu.de/root-server/produkte.php
(It seems like they only have a German page)
No windows server from them, though.