200K is not a large profit margin, you are a few employees' paychecks away from going under. While I'm sure you yourself would survive any technology shift and specialize in other related fields, the business might suffer. And these shocks are more and more frequent, it's essential to dig your heels in when you have a growth opportunity or expect to be amazoned out of your margin in a few years.

Ok, you say you don't know how to grow the business - how about taking that money and hiring somebody who does know, and move to a CTO / proprietor role. 200K a year should satisfy the immediate cash needs of a proven business man if you couple it with a good stock options plan. And if someone who could find work in a corporation for 500K accepts 200K and stock options, you know he's serious about growing your startup.

If you are looking for startups to angel, your own starup is the no-brainer choice because you get to the exponential returns on the rest of your assets. The only reason not to do that is when you diversify or you sense impending failure.