you are right, Poison the well are a hardcore sound, but because they inject feeling/emotions into their work other then just base 'rage'.. a descriptive word as 'emo' can be used, that does not make them an 'Emo' band, although if you go back to the begining of the term 'Emo' it was used not to represent 'boy bands'.. emo kids, but was used to differentiate between the hardcore punk sound that started in the early eighties and those that put more artistic ideas into their music. ie: punk hardcore evolved into emocore/screamo & metalcore and continues to evolve. PTW helped create the sound that they perform and which has evolved into the many guise's of 'core sound's you hear today..
If anyone else can articulate it better/disagree, please reply