Ultrasound Amps - I have not played a gig or recorded a single song with an acoustic guitar in the last 10 years and not used either an ultrasound amp, or DI.  The amps are perfect for small and medium sized rooms and in my humble opinion the DIs are the best on the market.

I currently use:

CP100 - is my go to amp... mine has several hundred gigs on it and not an ounce of trouble.

DS4 - nice wide sound, hard to believe it is only 50w!  I have this one and two of its precursors, luv them all.

DImax - This little bugger is amazing... 2 DIs in one!  Most folks bring more than one guitar to a gig, this allows you to plug both of them in and have total control of your tone from the stage.