Does your guitar sound dull, even with new strings? Assuming the strings are fastened to the machines and seated at the bridge properly, and the nut and saddle are in good order, a set of brass bridge pins (see Stew-Mac reference above for a source) will brighten the sound for alot less coin than a new guitar.
Does your guitar sound dull still? Maybe the top is overbraced. Try a slightly heavier set of strings, like medium-lights instead of lights, to drive the top a bit more. Be careful not to overdo this, it could cause some distortion in the top and cause the opposite effect.
Are songs written too high for your vocal range? Try tuning down a half or whole step and using the same familar chord shapes. This may require a slightly heavier set of strings. Just capo up if you need to play with others who can't/won't adapt. The other advantage of this compared to capoing up and/or transposing is you won't loose so much of the bass range of the instrument. (An aside here: I keep a guitar tuned a minor third low (3 half steps) and strung with heavy strings. It's also a bit longer scale at 27 inches. Sounds fantastic.)
Is it hard to balance your guitar on your knee or from the strap? A strap with a rough surface (like the underside of leather) against your shirt will grip better than a smooth surface. Machine head knobs can be replaced with ebony or plastic (faux pearl is nice) to reduce the weight of the headstock which is increased by the leverage of the neck...metal knobs are heavy. Some find it comfortable to tie one end of the strap to the headstock which moves the centre of gravity to a more balanced place, and has a more old-time appearance. A wider strat may also be more comfortable than a length of rope. But to each his own.
More later. Mooh.