I always run in the PA. We all do. It helps for "presence" if everyone is in the PA - even if it's just a touch - like our drums.
I'm a big PA supporter. Stage amps are for your own monitoring.
+1. But understand that, at first you can run a touch of your bass (and everything else) through the PA, still planning on the audience hearing you primarly from your stage volume (your amp). So it's really just common sense, you're using the PA for vocals, at the correct volumes and you intentionally run any instruments, including your bass way below the vocals and I'd run everything flat. You can just barely hear the bass out of the PA, and the only time you would notice the bass in the PA, is maybe if you took it out of the PA mix - kind of a "what just happened?" feeling. It just has that presence in the PA. As your band progresses, and you either learn how to get a good mix from onstage, or you get a sound man, that's when you shift to your amp being your monitor, and the audience hears you out of the PA - you want your stage volume to be as low as possible now. I will also say though, that even though it sounds excellent for the audience to hear everything out of the PA and hear nothing from the stage (in a perfect world), it doesn't sound bad for the audience to hear kind of a mixture of what's coming off the stage, combined with your PA mix, and in many cases that's how it will be anyway because you just can't control the volume of drums, etc.
One thing I'm also learning, is that when you are running out of the PA - like any other band, on your first break you'll either hear from people, or you'll ask a friend how things sound. When I hear something like "I can't hear the bass", instead of turning the bass amp up, we bump it up in the PA instead. This way it forces you to begin heading in the right direction of having the audience primarily hear your band mixed throug the PA mains. When you do this, you eliminate so many headaches of trying to sound consistent in all the unique clubs, some where, you sound fine to the people over there, but the people way over in the back on that end, it doesn't sound very good. Running through the PA = consistent band sound.
I've been in situations where they had me turn down so low, that even though I knew they were getting a great PA mix, it was no fun and not inspiring to play. You need to be able to hear yourself enough so you're enjoying it yourself, and the rest of the band is getting off on your playing too. That's just my opinion.
Last, I'm the farthest thing from a PA expert, but one thing I think I've learned, is that, you get a much better PA mix sound in most of the clubs you'll play in, if your mains are 3 way and not 2 way. Having that 6" or 8" midrange speaker gives you that intimacy with the audience who is very close to you.
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