Tripod head question.

My brother, who isn't on here, is into astro. He sent me this today. Any help would be appreciated. Thanks in advance.
Morning mr, about ready for Xmas? I need your help, could you ask about & see if you can come up with a geared head for my tripod, I think I'm going to try astrotrac with my Slik pro 700dx, I've been advised to look at the manfrotto 496 rc2 but I'm not sure if I'd need a different tripod too? it's not money that's the issue I'm just confused!!

http://www.ephotocraft​.com/itemdesc.asp?ic=7​19821287681
http://www.adorama.com …KuArpfyrbQCFQUF​nQod4EcAaQ
these are both geared heads. They offer fine tuning of the Alt and Az axises. These geared heads mimic the movement of the astrotrac wedge http://www.astrotrac.c​om/Default.aspx?p=wedg​e When using the astrotrac it is necessary to adjust the angle of the unit to the appropriate latitude of your location in order to polar align with the north star. It is also necessary to be able to rotate 360 degrees in order to locate objects in the sky. The geared units allow you to adjust latitude in fine tuned increments.

Thanks very much for an excellent, detailed reply. I shall pass this on.