I think that I'd buy QuickenŽ ... and if necessary, a Windows box on which to run it. (Or AccountEdgeŽ for a Mac.)
I frankly wouldn't make "Linux" the ruling-constraint here. Find the most appropriate software for the application, then purchase a computer of an appropriate configuration in which to run it. If that computer is dedicated just to that particular task, then so be it. Computers are cheap now, and a used one will do nicely.