The motherboard I've been testing the past week paired with the Ryzen 7 1700 is the MSI B350 TOMAHAWK, a board in short supply that will set you back only $110 USD.
I purchased the MSI B350 TOMAHAWK as the motherboard to go with the AMD Ryzen 7 1700 when racked up in our Linux benchmarking farm. What attracted me to this board was it being among the cheaper Ryzen motherboards at $109 USD while still having all of the features I needed out of this particular test system.
This board supports new AMD Ryzen processors, up to DDR4-3200 in its OC mode (though I haven't had any luck running it with high frequency DDR4 in AMP mode), M.2 NVMe SSD support, USB 3.1 Gen1 Type-A and Type-C, and other features that make it a fairly decent board for its price. More information on this board can be found via MSI.com.
Over the B350, the X370 chipset supports six USB 3.1 Gen1 connections over just two on the B350 while both support two USB 3.1 Gen2 connections. The X370 also supports four SATA ports but only two on the B350, 8 vs. 6 PCI Express ports, and no multi-GPU support. For those on a budget, the B350 chipset isn't bad and still more capable than the A320/X300.