Well, definitely do not go 1900x way, as its the same 8-core CPU as 1800x, except you would need much more expensive motherboard for it.
Yeah, I researched that option and decided that it wasn't practical on the budget I'd worked out, at AUD$1500. Yes, I went over by $123.00, but I also included the graphics card and it's acceptable. Had I gone the 1900x way it would have exceeded AUD$2000.00, and I wasn't prepared to go that high. The 1900x motherboards alone began at AUD$660, and with the Ryzen1900x starting at AUD$729, I'm getting more bang for my buck going the 1700x way. I am choosing to go with a package deal that bundles the Ryzen 1700x with and an Asus ROG Crosshair Hero VI, which saves me a few bucks going that way.
BTW, what is the main purpose of your computer? If its gaming, rather than work, you would be probably be better served by Intel Coffee-Lake platform. Dont know about price difference against 1700x, but high clocked six-core Intel is definitely better choice for games than lower clocked 8-core AMD, bar maybe very few specific cases i guess, like AotS . Even though you like AMD and want to support them by your purchase, which is commendable, u should know you might be doing that at your own expense.
I don't do a lot of gaming, just a bit here and there, but none of that high-end RPG stuff. No, I mostly mess around with music and video editing, etc, and the Ryzen 1700x will more than adequately suit my needs. I did look at an Intel build but the combinations I considered came to more than the Ryzen build without the graphics card. With the Ryzen I get the graphics card as well, and for around the same price as the Intel build I researched without a GPU.
As for supporting AMD, well I guess that's a part of it, but it also comes down to what I can afford and what I feel is value for money. I've had several AMD builds over the years and been happy with them. I also had some Intel builds, starting with a Pentium II and then a P4. My current main PC has an Intel i7 4790K, and I'm happy with that as well. However, while it still performs well, it is aging some and I'd like to update to something newer.
Also, I have seen that the Ryzen 1700 series overclocks quite well, not that I'll necessarily bother, but I know it's there should I find the need to add a bit more grunt.