server-side solution as good as spam-sieve to clean webmail inbox?

Hello I purchased SpamSieve and use it on OS X with Mail.app and I love it. It is very precise after training, more than any other filter I used or tried.
My inbox at home is clean!

My only problem remains that when I check my email remotely (via webmail) I still have to deal with a ton of spam. My server has SpamAssassin but it doesn’t do a good job at all (setting 5.0)…
Does anyone know of any third-party solution that is as good as SpamSieve but works between the sender and my webmail inbox so that it can clean that and do it right?

Please let me know.
Thanks