Yep, a keyboard or drum amp would reproduce your voice the best. Guitar amps usually have some form of coloration that fits the instrument better. Although as Robert said, you can get some very cool effects by using a guitar amp. An obvious reference (and since it is the 25th birthday of it) would be the track "Something Against You" by the Pixies, off of Surfer Rosa. That is how your voice would sound through a guitar amp with some gain, as it is precisely how he achieved it. It may fit some tracks better than others. Notice the feedback. To hear it without the music, listen at the end where he says "I am one happy prick".