Nathina, it's really hard to comment on dulcimers without seeing and hearing them. And what one person thinks of as bright or mellow might not be what your ears here. I would suggest listening to dulcimer music posted here and on YouTube and Soundcloud. Most of us indicate the dulcimer we are playing and the tuning we use, and if we don't, ask. Then you can hear for yourself which luthiers make instruments that appeal to you.
For what it's worth, I have never played or even seen a Gardener, but I own two Ewing dulcimers. However, neither is a full-size instrument. One is an octave dulcimer and one a 3/4-size instrument that Ron calls a "baritone dulcimette." I love both of them for their balanced and clear tone and the responsiveness of the fretboard. Ron's dulcimers are of very high quality and his baritones in particular enjoy a fine reputation.