Concept is a mixed bag, but to keep it short, you get what you pay for. If going with Concept, only deal with Dave (owner). And yes, you have to hand-hold them through the build process, but the prices are far lower than anyone else. My build thread has some comments on the experience, it wasn't smooth but they were in a bit of a staffing change-over since the main tank builder to deal with (Denny) passed away.
I am overall happy with my tanks, but there were some things overlooked / not as I expected, with the sump specifically.