Zork,
My last A/C unit form Lennox wasn't very good. My A/C contractor switched his tie-in and went with Trane. I've had the new Trane for four years now, and not a single problem of any kind - and it cools and heats our two-story house very well. You might want to look into Trane. My unit ended up at $7000 installed - heat pump, new evaporator, and all the trimmings (in Arlington).