Stereo imaging sounds fine for the single acoustic guitar, the VSTi/synth strings could use some reverb to give them 'room', bring up their volume a little then keep them spread wide and reduce the width of the guitar for contrast. You could even record the strings 1 line/note at a time per track, so your could spread them across the stereo field. Should work on technique to remove some of the finger squeaks - ever try coated strings?