Ask HN: under-paid, when to leave?

Facts: -Have been employed by co for 5+ years -Hired as a programmer, but now do programming, embedded systems hw engineering, network security assessments, and computer forensic consulting, -25 years old -Masters of science in software engineering (graduated this month)

The issue is I feel I am underpaid, after my post-graduate raise. The root of the issue is that I enjoy and like my job so much that I do not want to leave, at all. I am told and do believe that my boss is unable to pay me what I would like and think I potentially deserve (double what I am making now), but at the same time I do not *know that he is paying the maximum he can while still surviving. Even more, I have trouble thinking of more than one or two ways to pressure him into the maximum, other than show-boating another co's offer for me to him.

I do realize interviewing for another offer would solve the question of what I deserve, but I am so torn on leaving for something new. My idea is that change is good, embrace the uncomfortable. But two reasons compel me to stay: one, I love what I do, especially how dynamic it is and I do not want to pick a niche. I imagine that moving to a new company would require choosing a position in either programming, forensics, or network security, not all three. Two, I have always seen this job as a 'run away train' or 'shortcut' - in other words, it seems the smart move is to start your own company, and as I am one person removed from the owner, and have (unsurprisingly) been offered partial ownership of the company, this potentially can be a trade-off for salary.

I wish for some mentoring from those with experience with this. How wrong is it to stay in the same co for more than 5 years at this age? How long do I stick around and wait it out before it is too late?