So many variables on an acoustic (more so than an electric, IMO) as in what type of acoustic, woods used, scale length, strings used, etc.
Is your question just a general one or for a specific guitar?
Bass is going to come from the size of the body and the top wood. Thicker strings might also be a help but I would be careful going big with strings if you do not have a truss rod. Your best bet would be buying an acoustic with more bass. Ibanez makes beautiful budget acoustic guitars. Mine cost $500 check out my review.
http://www.tmrzoo.com/2012/35842/gui...lectric-guitar
Mostly in general but I have an applause and an old nylon string that are really weak and thin sounding.
. I had a nylon string years ago and I made a bridge out of ipe wood and it was like night and day.
I'm skipping bone and going with Tusq for acoustics from now on. I've had bone nuts that have been uneven sounding, volume-wise. Tusq may be a little warmer and more expensive, but the results are very repeatable. You basically know what you'll end up with.
As far as the classical/nylon string ace, try going with D'Addario Pro Artes in high tension. It'll be bigger sounding, if a little brighter.
I prefer Tusq to bone on acoustic guitars. I've found bone to be less consistent tone-wise - while always enjoy the sound of Tusq.
I've got a set of mediums that I haven't put on yet because I want to tackle the saddle & nut problem at the same time. I've got regular D'Addario strings on it now.