Should I ask for a replacement?

I've now had my m15x for over a year, and have been very satisfied

The thing is that a few months ago it started lagging on video and audio a few seconds once every 5-20 min when playing games and watching movies.

I've been talking to support a lot lately, and they have been very helpfull.

Here is what I've done so far:
Crosschecked the ram
reinstalled windows
run some diagnosticstool from resource cd

None of the above helped, so dell sent a tech to replace mobo and HDD.
This didnt solve the problem either, so they had me send it to their workshop.

I just got it back, and it says that they replaced the gpu, the gpu-heatsink and for some reason the palmrest (which had been replaced just a week earlier by the tech who did the mobo).

I turned it on and watched a few episodes of how I met your mother, and sadly the problem still persists.

Im pretty tired of having to call back and forth and have parts replaced, since nothing seems to help.

Should I call in for a replacement, and in that case what should I accept?
From previous threads I can see that I should accept nothing less than the
m17xR3.

The thing I wanna know is what processor (seeing as this is sandy bridge, and I dont know how to compare), gpu, ram and everything else I should accept, and what arguments should I use to get a 6970 instead of the 460. Like is there any argument that will help make it necessary for me to have an ATI card over Nvidia?

Edit:
Oh yeah. My specs are at the bottom in case you missed it

 

Just tried to build a m17x on the danish alienware site. They dont offer the bluray read and write, but only read. What should I ask for instead of that? Should I go for more RAM, a better HDD or maybe a better wifi-card?

 

try using a registry cleaner or something, hell pop open task manager while you do that. this is starting to sound like a resource hog program not a hardware issue. my last desktop lasted me for 4 years and change and was only replaced cause I think my GPU overheated and I wanted something possibly portable.

 

But shouldnt an issue like that be solved after 2 reinstalls and after swapping to a brand new, clean harddisc?