We use Fiery XF with x900 printers with great success - accurate proofs all the time. We've used ProofMaster some years ago (until version 4) which is also a great product. At the old days, ProofMaster included an Editor, too, which can be used to make alterations to PDF files (and accurately softproof them), which can be a great plus. It's worth investigating whether they still have this proposition. Serendipity is also offering a RIP product for x900 printers (Blackmagic).
When investing, please be aware that the weakest link in the system will be the printer. You might throw 3000 USD or more onto the software, just to find out that the print heads clogged and then damaged themselves - a service cost of 1500-2000 USD, minimum. Daily printing (to get fresh inks into the head) is a must with x900 devices.