Help me choose next calculator

[dockthedog]

My beloved HP 48GX died. I'm thinking of either an e-bay direct replacement of my 48GX, a new 50G or a new Prime. Please help me decide. Here is what is and is not important to me:

Features I want, in order of importance:
*RPN is a must
*Easy unit conversion, which is available on my 48GX, is very important to me.
*It would be nice to have something that handles fractions such as a construction calculator would. My 48GX does not do this but it would sure be nice to have. Maybe the prime will have an app avilable for that.
*Time Value of Money calculations

Features that I don't care about
*symbolic input or solving symbolically
*Graphing
*That it's allowed for testing


I am an engineer, not a student. I am not likely to ever be a power programmer of the new calculator, just simple function definition is probably all I'll ever do.

Thank you!