4th time, same issue, refuse to replace

Purchased an Alienware R16 in December and have had nothing but problems where it randomly restarts and although it lights up on the tower, I get no picture and the monitor no longer recognizes the input. I've also seen random mouse movement and other glitches.

On this fourth time they're going to send a guy out again to replace the video card which didn't work the first time and is not the problem. Motherboard has already been replaced. I've spent countless hours on the phone with technical support and they just keep on going through the same script and giving me the same answers. It's very obvious to me this computer is a lemon but they refuse to replace it. It's costing Dell more and more money to keep trying to repair it... yet nobody cares. I've bought countless computers from Dell... never again. I just don't understand why they refuse to replace it. Heck I'll buy a more expensive computer if they would credit me... I'm not asking for a refund. 

Somebody please help.