If youre looking in that range, I might as well start taking pre-orders for my M.2 accelerator since its ready. It has a 200k LE 7 series chip and 1GB of DDR3 + 4x PCIe (2.0 atm). $329 for the very fast version, $199 for the lower end (100k LE/512MB DDR3). Uses a M.2 M-Key / Nvme slot, or a $10 PCIe adapter.
How can I order this board? Can you share more infos? (Algos, hashrates etc...)