Well I have no experience actually setting up this but some high power routers/access points with high gain antennas would probably be preferable (at least if both sides use comparable hardware). I don't know how well the software stands up from software such as Amped Wireless equipment but they'd probably be a good from an hardware standpoint. But it might be cheaper jam wifi-cards in the already available computers and running local software.
I once needed internet access from an server with no physical network access, however I had an friend living across the hall (quite thick concrete and brick walls but hardwood doors). That time I were rather successful running two cheapo PCI wifi-cards with external antennas I had laying around. Used lagg interfaces (link aggregation in failover mode) in FreeBSD and got a workable remote terminal session over mosh. It wasn't optimal but it certainly worked.
I once needed internet access from an server with no physical network access, however I had an friend living across the hall (quite thick concrete and brick walls but hardwood doors). That time I were rather successful running two cheapo PCI wifi-cards with external antennas I had laying around. Used lagg interfaces (link aggregation in failover mode) in FreeBSD and got a workable remote terminal session over mosh. It wasn't optimal but it certainly worked.