Congrats and enjoy! It is nice to have a different top wood even on a similar body. Your GC3 would be a 312 in current nomenclature. I would expect the 314/324 to sound slightly bigger with a hint more bass due to the wider lower bout, but that is not a universal thing. Oddly enough, the GC body is the only Taylor shape that I have not owned. Not that I don't like the Grand Concerts, but my main acquisition phase was mostly complete by the time I became more interested in shorter scale, smaller body guitars. I'm a big NFL lineman sized guy, and the GA / x14 size just seemed to fit me better. Especially back in the days when I rested a guitar on my right leg.
These days old sports injuries and orthopedic surgeries have caught up to me and I must play seated using a strap in the semi-classical position. Unlike a few years ago, I can once again play any body size about equally well. Relevant to nothing, the single best-ever Taylor guitar that I have played (out of hundreds) was a 522 twelve-fret about 3-4 years ago. I came very close to buying it.
