Jrgns,
Clamav is about the best GPL AV scanner out there for SME. What is it that you don't like about Clam? I've used several AV scanners on SME over the years, both commercial and GPL. Clam does a fine job at detecting viruses, is activily developed, and has fairly up to date definitions. If you are looking to step up from Clam, then I think you need to be looking at a commercial solutions.
By far and away, the best AV scanner for SME that I've used is Virus Wall by Trend. This is the scanner that comes with Mitel's Servicelink package. It would be wonderful is someone in the community, nudge nudge, would develop a standalone contrib for Trend's Virus Wall. My guess is that it wouldn't be that big of a task to do using one of the currently available contribs as a starting point.
Darrel May has put together a turnkey commercial AV scanner for SME called BitDefender. BD is a fairly good scanner, but is about on par with Clam IMO. I would only purchase this scanner if you really want the comfort of a commercial solution though.
As far as an alternate to spamassassin, there are numerious options available depending on what level of spam prevention you want to implement.
Good luck.
Greg Zartman