hi, I've been making studio monitors and amps and lots of other electronics projetcts for almost 2 years now.
And while it does cost me a lot less to build than to buy brand new, this was not the case for my first project.
It takes a lot of time and work to get this kind of thing right, especially the first time around.
But, its definitly a great project and will make you understand a lot more how your sound is created.
Oh, of course, you can make extremly excellent speakers with the exact configuration you need frequency wise and all.
hope this helps, let us know what you decide on doing!