I have a SSD VPS with KnownHost for my own sites, but I also have website clients on other web hosts ranging from shared to VPSs. I've found that SpamAssassin is getting less effective at managing spam, I'm seeing that both with clients and my own email. I realize there are some strategies you can set with SpamAssassin to train it, but that is often tricky to setup. Many other hosts are now integrating the SpamExperts service with their plans or offering as an add on. I've found it to work great. I would highly suggest/request that KnownHost integrate or offer SpamExperts within cPanel on VPS accounts. I'm assuming this is technically possible. While I've been very happy with KnownHost, I would consider moving to another company that offers more robust spam filtering.