The A7V133 is the KT133
a chipset and is compatible with the XP1600 CPU. In fact, I am running 1900+ on my A7V133.
Now your gigabyte mobo is another story. According to gigabyte web site, there are 4 different revisions of that mobo.
DETAILS: PCB revision Chipset Support FSB
7ZX(-1) rev.1.0 VIA KT133 Chipset Support 100MHz FSB
7ZX(-1) rev.5.0 VIA KT133 Chipset Support 100MHz FSB
7ZX rev.5.1 VIA KT133A Chipset Support 100/133MHz FSB
7ZX-1 rev.5.1 VIA KT133(E) Chipset Support 100MHz FSB
If you have KT133a version, then it will probably work. Otherwise???
http://www.gigabyte.com.tw/products/7zx.htm