I had been using the UAD precision limiter, it did exactly what I wanted it to do: set the absolute maximum level without distortion or overs. Normally I barely tickle it but it's nice to have on the master. I stopped using my UAD-1 card because it was causing all kinds of problems with X3. I've been looking for something that works as well, for now I'm using the Concrete Limiter but it doesn't seem quite as transparent and the Blue Cat limiter seems to pump a little too much. I don't need a multiband or anything fancy, just something to keep the mix under control.
Any suggestions?

You may want to try the free demo of FabFilter Pro-L If you like it and are a first time FabFilter customer, there is a 10% discount available from any existing user.

Try the FabFilter Pro-L demo.

Concrete Limiter is not transparent? That is news to me. You can switch on the bass switch to add a bit more bass but beside that I find it very transparent.

the "Boost 11" limiter in Sonar is actually not terrible - I don't know if I'd put it on the master bus, though.

Might also want to look at A.O.M. Invisible Limiter
 

scook
You may want to try the free demo of FabFilter Pro-L If you like it and are a first time FabFilter customer, there is a 10% discount available from any existing user.

+1.  Most excellent.

Voxengo Elephant.

I use mostly UAD precision limiter or maximizer
Try also:
Waves L2
Voxengo Elephant
Limiter6
 

The T-Racks Brickwall Limiter is probably also worth a look. Great inexpensive plugin.
 
Dean