I have used William Turner with a of of inks and use a RIP to control. It has an excellent black and can take a lot of ink, I've rarely seen it shoulder over before actually bleeding. I've exceeded 1.7 with certain ink setups and the RIP.
It may still never match the dmax of EHPN, but it exceeds most of the available papers.
With the RGB driver your options are to test every viable media setting, and whatever density adjustments are available in custom driver settings.
William Turner can produce gorgeous, but very physically delicate, prints.