EnGenius is "the" long-range phone. They do what they promise.
At a local 8,000 seat arena, I have a set of the Uniden TRUxxxx series phones in my office. As long as I have line-of-sight with the unit, it works everywhere. When I go below the seats (concrete slab), I'd say I can reach about 3/4 of the concourse. For the $30 I paid for them on clearance, they're an absolute bargain. I also use the Uniden TRUxxx series phones at both of my homes. Well-built, good sound quality, good speakerphone. Both homes run off an IP phone system (Cisco & Aastra hardwired IP phones), with analog adapters powering the Uniden systems. Haven't tried any IP phones yet.