If you like the sound of your yamaha why don't you just add a pickup to that guitar? There are pickups that just snap into the soundhole of the guitar and are easy to install/remove, or there are other types that install inside the guitar. Most of replace the strap button of the back of the guitar with the cord jack so you don't have to drill any kind of hole in your guitar. Most acoustic guitar pickups are just piezo-electric pickups so they aren't anything really special.
I've found myself that amplifying an acoustic really only makes sense when you want to send the sound over a PA system; the problem with using any kind of amplifier is that any change to the sound, like even a fairly neutral amplifier will do, will sound rather annoying since the sound of the guitar itself will still kind of over-power the sound of the amplifier; creating an echo effect that is rather annoying.