Alert!
Alert!
I am a EFI reseller, and never heard CPXFv4.1 can be £70; you had better verify your dongle# and license# w/ your local EFI dealer. If you're getting a cracked version, it's quite possible that it won't do auto updating as orignal users enjoy not to mention upgrade or tech support.
If you have verify the software's authenticity, then congratulations!
The advice I would have is to go for EFI's Proofing paper itself for best delta-E on both CMYK and Pantone.
If you're using 3rd party paper, you have to be extremely pro in order to tweak the epl/icc to match the original EFI proofing paper.
Ultrachrome K3 ink as compare to K3V2 and latest HDR ink has minor shortage for color gamut as pointed out by GMG, you'll need high grade paper in order to enjoy the best delta-E as x880 and x900 printer.