I print my own on an Epson 7900 up to 24" wide. Larger than that (rare), I send out to White House Custom Color. I've printed a pretty fair number of DX files at 24x36", both myself and at WHCC. I'm sure I could go bigger, but haven't needed to with any DX files. I've printed a few bigger than that from FX, also from 12mp or so.
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!