I've ordered lots of stuff, from lots of places, and have my pros and cons for each.
Sweetwater is great if you need any kind of assistance with anything you buy. They offer the most support, and will bend over backwards to make sure you're a happy satisfied customer. Only 2 reasons they don't get more of my business. First, is an issue we resolved... they will call you, relentlessly, unless you specifically tell them not to. Some people like this. I didn't. Had they not done that early in my online buying days, I'd have probably used them more. Other reason I don't go to them first is that I am always looking for the lowest price, and they're the toughest to haggle with. In fact, I don't think I've ever gotten a best price out of them. I usually now buy from them only when I can't find something somewhere else, OR, if their listed price beats someplace else.
Americanmusical (same company as zzounds) is my favorite for several reasons. I like the easy payment plans that most other places don't offer. I get the quickest delivery from them. I seem to get the best customer service from them, but that could very well just be the luck of the draw. Only drawback with AMS is that they don't always have what I'm looking for.
Musiciansfriend (same as music123) is where most of my business goes. Best price is almost always the reason. I just about always have a 20% coupon to use, and if not I can wait for one. None of the other companies offer that, hassle free - although they can often easily be convinced. I've had my issues with MF, but it could be because I've ordered from them most. Every issue was resolved, and I was always left a happy customer. Same with the other places mentioned. Only place I ever bought from online that I was up an unhappy customer with was bass northwest. And I will never buy from them again.
As for price, and having a "friend" or contact at any of the online companies, it's not necessary. Any sales person can give you the same price as these guys. What I do now is take what I'm interested in, knock 20% off, and make them an offer for that price. They usually check, and can often do it. If not, 15% off is almost a guarantee. Most places have 15% off sales every other week anyhow. There are a few items that can't be budged (ipads, certain hot newer items from the big companies), but most prices can be cut significantly. And if anyone ever pays full asking price for a Ric, they need to have their heads examined.
Sorry if anyone here did, but they'll drop thousands off the price without even thinking about it.