WHERE??? hook a brother up lol. Actually I will buy one too if we get to them before they are gone. What I would do is buy the internal and you can always add the external I THINK. I have fooled around with them but not really used them for lengthy periods, but I love their screens. This unit is the greyscale if not mistaken. The thing I realy like about them is it is pretty much an all in one unit and it has good fuel management attachments. These have been around for a while over in New Zealand, 1988, and they accept c-map http://www.c-map.com/index2.html
and a comparison can be found here.
I would get with them about clarity through the T-top but I would imagine it would only minimally effect performance of the unit if at all. Also, check ebay for the external antennas.