Would it be crazy loud if I just ran straight pipes out the back from the headers?

As mentioned, straight pipes usually sound like crap, especially on stock engines.
You'll be the laughing stock with people in the know, and mostly being considered annoying by all others.

Also engines don't need 'backpressure' from mufflers. Every engine will run better with less resistance on either intake or exhaust side. Thing is the engine has to be tuned for it.
And before some dip mentions an engine will run crap with no exhaust at all, yes that's true because an exhaustsystem is there, besides occupant-health and car safety, to help scavenge exhaustfumes from the engine.

I'll be installing a pair of Borla ProXS mufflers very soon on my Dart.
Kinda curious how they sound with a pair of Dougs Headers and 2.5" full X-pipe exhaust system.