I owned the GT55 for a while and wanted to love it, but just didn't. I like chinese condensers for my voice. (I also thought I liked it for a few days, but it takes more than that for you to bring up the old mic)The GT55... a lot like the AT3035 for me was just too dark... the vocals I recorded didn't sparkle. It's preference but I want to sound dynamic and pleasant, and against the hate your own voice tendency, the studio projects c1 and behringer b1 type thing works for me.
So if it was me, if the GT66 is anything like the GT55 I'd go for something else before.