Personally, I would never buy a prebuilt, but that's just me. I've been building for years, and not only do you get exactly what you want, there's a measure of satisfaction involved.
You could also have a local builder do it to your specs. You'll pay more, but again, you'll get exactly what you want, no more no less.
Hell, spec it out, send me the parts, and I'll throw it together for you. It's not like it's difficult or technical or anything.