Except for the music production and sound engineering, I do IT support and consulting so I know my stuff.
Originally Posted by kjypeace
... Get two DSL circuits and team them at the server...
I am sorry but this is not working 99%. To make it work, it has both lines to come from the same provider and to be bridged at the provider too. If it is offered it is going to cost extra. If the lines are from different providers, then only load balancing and redundant failover are going to be expected as benefits but they have to be supported by the router at your facility.
In other case the upload is going to be the bottleneck, that is why is called Asymmetrical DSL (aDSL). You may consider sDSL (symmetrical) but they cost more.
An other solution is wireless and I mean at a municipality level. If you have optical contact between the two sites it works. If not, you may have to add another or two stations in between to connect them. You need high gain antennas and weather proof boxes to put the little equipment on the roofs. You can check the equipment at Fleeman, Anderson & Bird, Corp.
There are many other places too.
Check also wireless networks at municipality level at NYCwireless FrontPage - Seattle Wireless Internet Archive: SFLan
Also check the local laws and permits. More common is free or for a small fee. Then the cost is only for the equipment. With 801.11b equipment you could have up to about 5mbit bidirectional and with 11g or 11a about 25Mbits. With line of sight and small number of wireless networks at your area, you could cover from 5 to 10 miles per link easily. So you could go very far.
On the wireless side there are also laser links but they are very expensive and usually they cover about 2 to 5 miles.