Scubaboy
Let me tell you a story about someone much like yourself. Stating a nonpassionate marriage, but planning to stay in for the children, this guy put out an online personal ad. He didn't use his own picture, but someone that looked similar enough. He was delighted when a lady responded that was in the same situation. He figured - no complications, since she wanted to stay in her marriage also. She sent a pic and he thought she was pretty hot. They exchanged emails and IMs that increased in intensity until they planned a meeting. Imagine his surprise when the woman that met him was his wife. She was also surprised.
Instead of using this rekindled heat to save their marriage they ended up in a huge, drawn out, bitter divorce.
Maybe you should try to rekindle what you have and if that doesn't work get out before you start looking for a replacement bed partner.
In the real world, people who want to stay married and cheat are really just scared of being alone. Anything else they say is a lie.