SME IV or Wilson-Benesch Act .5 for Linn LP12?

You can't go wrong with a Linn arm in your price range. Used Ittoks in good condition are excellent, also.

As I recall the SME is not compatible with the Sondek. Don't know about the Wilson arm. I'd go for a used Ittok or NAIM Arro. Stay away from used Linn EKOS arms as they have bearing problems.

I'm surprised to hear of anyone wanting an SME IV! When I had one umpteen years ago, people were dumping them used for about $50 Canadian. The problem with them, as dealers told me, was that SME had backed the wrong horse--light weight cartridges that would track at well below one gram. When heavier and much heavier-tracking moving coils came into ascendancy, the SME IV was horribly unsuited to them. Their "bearing chatter" was said to be horrendous.

I'm just passing this on, since I'm not competent myself to speak authoritatively. Still, I'd check VERY carefully before investing in what I believe to be an arm that missed the boat, if I may change the metaphor from horses.