Antispam module works well, and is more than functional enough not to need SCAMNET which does not add much in the way of functionality, you are better off with just the antispam module.
Use the IP table to block repeat SPAMMERs, this will reduce the workload and can almost eliminate the problem. Also keep users that SPAM blocked in the IP Table even if you delete/disable their account, they usually come back and create new accounts.
Be mindful of the settings, you do not want them to be too restrictive as your user will stop using the site.
Suggested settings to start off using: They will get you up and running with minimal interruption to regular users, each site is different so tailor these to suit your needs:
General: Do not enable: "Total block all spam content"
IP Table: "Allow all except listed"
Akismet: We mostly have this off as it blocks too much regular content.
StopspamForum: Enable works well
Profanity Filter: Works well, add words as needed.