L.R. Baggs M-1 passive pickup through a Para Acoustic DI Preamp will work wonders on a lower-end guitar and do the proper justice to a high-end Martin, Gibson, Taylor etc.
The M-1 comes with a strap jack that simply plugs in to the pickup.
If you don't wantto drill any holes, or if you'd like the option of moving the pickup from one guitar to another, it also comes with a 12" cord that drapes out of the soundhole.
Very good stuff indeed.