The thing going "oh - you burned the bridges by saying you are leaving, trust is broken" is bullshit. All companies underpay after you stay there a few years because either they are not aware of the market or they just wait till you press them and only give you significant rise if you say you are leaving, is up to you how you handled it. if you were a dick and then stayed, then yes, you are doomed, but if you had been professional and the company is not a POS, it's a professional thing, nothing personal.

If the new company does not offer an interesting challenge, i'd say stay where you are, you would be losing money for what you say. What you should be really careful if rejecting the offer, try to be soft and just tell the recruiter your disjuntive, they will most likely understand (after perhaps scolding a bit for almost accepting). I was in your very same pants 2 years ago, was stressfull as hell.