Randy,
Do you have a clue as to the quality of the cable that is being used between these runs? If you cut the end of the cable off you should be able to look at the center conductor and if it is a shiny silver color, the video will struggle at your distances on video transmission. You would be better suited sending 720p video these distances and the closer distances under 750' you can run those at 1080p. Bear in mind that the quality of the cable will play into the effectiveness of the video transmission. If you cable is shiny silver in the middle it means that you have CCA or Copper Clad Aluminium cable in place and you can take 40% off on the distance to be able to transmit video as there is not enough copper in the cable to make transmission truly possible in HD. If you centrally locate your power supplies in each building, you should be a lot better off with your video quality.
Personally, I would simply put a recorder in each building with a wireless link back to the main off, then use the FREE CMS software on a PC at the main office to view all the recorders. There is a way to put an NVR at the main location and stream the channels into it as your central management device. In a situation like this, I would have smaller HDDs in the remote units and large HDDs in the central unit. The remote units having a small HDD will help, if something happens with the connection between buildings with the wireless link. The link we use heavily is our TP-LOCOM5 http://www.securitycameraking......-prd1.html .
I hope this helps you.