New to me but others might have already seen it but Hitech are now making a newer version of their 100mm filter holder. This one is aluminium and I've seen some reviews saying it's pretty on par with the LEE system.
I've ordered one from the UK so I will see how it is but I got the holder plus 2 wide angle adapters (77 & 82mm) for less than $150 shipped. So if you've been shopping around for a system this now complicates the process.
Cheers!