Ok, so I take it you are comfortable with the guitar as it is right? Then I would head down to a guitar store and ask them to measure your string gauges...string guage does affect sound, but if your current gauge is comfortable to play, that is the most important thing (especially as you are a beginner, most people quit because of bad action or heavy guage strings).

Ok, then you just have to experiment with different string types and brands...many things affect the sound, including materials,coating (if any etc) so a nickel string will sound different to a bronze string...and its up to you to find out which you like more...unfortunately, this is all personal preference, and what I like may make you turn away in disgust.

I personally like Elixer strings...to me, they play better and sound better for longer...but they are really expensive...still, I fit them to two of my guitars.

when it comes to acoustics, I like D'addario Dxp acoustic strings...they have quite a bit of punch, which I like...

at the end of the day though...you have gotta try out a few brands and materials and see for yourself what works best.

from what you describe, I would go with bronze strings...I find them warmer and less twangy than Nickel.

good luck