My 2c.

Tigerite - If you're looking at moving up to 55's, this is probably a good place to start. Mostly posts actual poker content, lots of recent posts about 55's and since he recently moved up to the 100's he obviously beat the 55's pretty solid.

ChrisV - Hasn't posted much recently but that's what archives are for. Though he plays well above the 55 level he has offered advice to players at all levels. What I really like about his posts is that not only is his advice excellent but he explains his thoughts very clearly and concisely. If I had to pick one poster who I thought would make a great teacher, it would be him.

Unarmed - If you really want to get good ... very thorough analysis at times, gets into situational analysis at a level I suspect most players, even winning ones do not even get close to when multi tabling. If you want insight into how a way above average player at the 100's thinks and just how many different things there sometimes are to consider in a given situation, he's your man.