parts that could cut costs:
the ryzen 1700X maybe 5% slower, but would cut $100. i probably would stick with the 1800x with this build though.
gpu, the gtx 1060 6gb or 1070 would be more reasonable and should still handle a decent amount of gpu fx. gpu performance will depend on how many gpu fx, and which gpu fx you use.
ssd storage, two 1tb 850 evo's in raid-0 would be half the price of the samsung 960 2tb. also you don't have as much expansion on ryzen for two m.2 ssd's, so i would stick with one m.2 only. some ryzen motherboards will have two m.2 slots, but the second m.2 slot won't run the samsung 960 m.2's at full speed. if you really want to avoid raid and you don't need 2tb of space for active/working projects, you could look at the 500g or 1tb 960 evo m.2. using a m.2 for the system drive is in overkill territory, a 850 evo sata ssd would save some money and perform similar. if you plan on leaving cache files on the system drive, it could help a little, but should also be fine on the media drive with the raid sata ssd's or m.2.
hdd storage, unless you need the capacity, you could use a single 4tb to hold all backups and misc storage.
cooling, skip liquid cooling. they go bad in 3-5 years and are much more trouble to replace than just a bad fan on an air cooler. an air cooler also avoids the chance of liquid leaks destroying other parts of the computer. the NH-D15 SE-AM4 is a good large air cooler that will be plenty and still reasonably quiet. it will need a big/wide case.
ram, 32gb should be ok and save money. you could go with 2x16gb to leave the option open for more memory later if worried about expansion, but that may limit ram speeds too. with ryzen you want fast memory, the faster the better. right now only a very few kits and brands of memory work with ryzen at fast speeds. i would talk with the place you plan on buying the system from, to make sure they can get the memory running at fast speeds, like ddr4-3000+. higher memory capacity and 2 sticks vs 4 sticks will limit those speeds, so you may only end up with speeds around ddr4-2666.
i don't have any vendors to recommend, but with some or all of those part changes it should be possible to get a build between $3k-4k from a reasonably priced vendor. the intel x99 platform with an 8 core cpu may cost around $500-600 more than the ryzen system. however its more refined at this point than ryzen, has more expansion options for more add-in-cards like the m.2 ssd's. and higher memory capacity. not everyone needs those x99 options, but its something to be aware of.
Thank you. This is very helpful.