How exactly do you "remind them who's boss"? Being boss doesn't just mean being taller and stronger. Being Alpha requires further mental manipulation. Have you any experience with Nothing In Life Is Free (NILIF)? NILIF is a simple training methodology that allows you to assert your position as alpha by requiring the dog to perform for ANYTHING he/she wants. If she wants to eat, she better be willing to sit beforehand or else she's going to starve for the day. Dogs will most likely submit to you before anything that drastic occurs, but NILIF is supposed to be a gentle way to assert your position.

5. NILIF -- Nothing in life is free. This means the dog must PERFORM to get anything it wants. For Gypsy, because we were trying to reduce dominance that was already present, I chose to use the "down" command because it requires her to throw herself into the most submissive posture available. I have since started peppering "sits" into the program, just to keep her paying attention -- but the dominance problem is long gone, so I'm less concerned with how submissive she is. "Wanna cookie?" -- nothing in life is free, so the dog must "down" on command for the cookie. (BTW -- when you start introducing NILIF, carry food AT ALL TIMES -- you're still rewarding the dog for submitting - this is NONCONFRONTATIONAL. Reward for a LONG time, then wean off food sporadically, but still praise the behavior.) "Wanna go outside?" - dog must "down". "Wanna drink of water?" -- that's right. You're catching on. The dog gets NO freebies. She must *earn* everything -- food (you should see her slam her body on the floor for dinner!), play, petting, water, going out, going for a r-i-d-e, getting T-R-E-A-T-S, coming inside. Gypsy even has to "earn" the right to work on the agility equipment ... partly because I think it helps her attitude ("Ohboyohboyohboy, Alpha-mom made me down, I must be about to do something Good"), and partly because she's so excited to be there that she needs the extra control.

BTW -- there are other non-confrontational ways to establish dominance. Ignore a dog when it tries to initiate play -- and as soon as it gives up, you initiate the game yourself. Alpha dogs decide when the pack plays, and when it hunts. And I *do* like the idea of teaching a puppy or a dog to roll on its back and accept petting ... but it doesn't have to be a battle.
Also, I have heard that females tend to be more nippy than males, but I know this does not hold true for every breed. I've been through this with my dogs too, so I can feel your pain!