Yep, the Sig 556 is probably one of the better "non AR" options. Heavy and somewhat expensive though.
Some of the Century Galils now work fine. Early ones had some problems, and there was actually a recall. Well, okay, maybe "fine" is an overstatement. It is Century after all... They're turning out guns that either work okay or can be made to work. Still not really worth what the asking price is.
Buying an IMI, well you're paying an awful premium for what you're actually getting.
Unless you convert a Galil to use AR mags, you're stuck with either expensive steel mags that might be beat up, or mildly less expensive Orlite mags that might be beat up.
The Izzys replaced their Galils with M4 clones. That's why they sold the parts off as surplus and Century can do their builds.
If you want to be different, get a Remington 7615 pump with the collapsible stock. I had one for a while. Sort of pointless, but different.