I bought a used X230, upgraded to 16GB of RAM, added an SSD, and it's been an awesome machine so far. But you're right, the X250 will offer a better display. At least Lenovo seems to have eased up on the hardware blacklist where this model and the T450 are concerned http://www.reddit.com/r/thinkpad/comments/31rnsv/t450_and_x2...

Also, here's a link related to the 16GB SO-DIMM modules that you mentioned https://forums.lenovo.com/t5/X-Series-ThinkPad-Laptops/16GB-...