First of all thanks for the replies and guidance, really appreciate it. I'm still quite undecided though, the Nikon 14-24 is unfortunately too pricey for me to even think about..
It seems as though the general consensus on the Sigma is the optical quality is not up there, but I don't really know what else to go with... maybe the 17-40 f/4L a better option? Certainly still within my budget.. but it does bother me that it isn't quite as wide as the Sigma.
It's a shame there seems to be a shortage of options for wide field FF lenses..
