I just ordered a Transcend SATA III 6Gb/s MTS600 M.2 SSD 256GB used card from a vendor on eBay for $75 shipped. This appears to be the same brand as the 128GB Udoo offers in its shop. Transcend provides a utility named SSD Scope available for download here: https://www.transcend-info.com/Support/No-643. There's also a FAQ and Product Installation Video accessible from that page. Jetguy has provided some benchmark information in this thread: http://www.udoo.org/forum/threads/m-2-ssd-vs-emmc-for-os.6702/
