XPS 15 (L521X) Throttling issues

First off My current computer is a XPS 15 with an  i5-3210m, 6GB RAM, 500GB HDD, and a GT 630M 1GB Gddr5. This computer serves as a replacement for my old model XPS (L502X) which had an i5-2430m, 8GB RAM, 640GB HDD, and a GT 540M 2GB ddr3. To be honest the L502X had already been replaced once by Dell, and the original system only had 6GB RAM, a 500GB HDD, and an i5-2410m (Same GPU).

 I received my new laptop at the end of July and immediately noticed how much nicer the new machine looked. Upon booting up the machine a couple of things jumped out at me, the most important being that the machine resembled the machine I initially purchased from Dell more than the replacement machine I received. I quickly decided that I could deal with less HDD space, 2GB less RAM, and 1GB less vRAM; only if it performed the same or better than my old machine. I quickly set up the 2 machines side by side (my old machine was being sent in for USB issues, it could still run games) and booted up a couple of games, making sure that the settings were the same on both machines. I ran each game for about 5-10min closely monitoring FPS in various situations. I know that this is not the most scientific way to approach this and I could have done several tests that would have given me a better idea of the 2 machines performance. The new machine performed as well as the old machine and in some games was able to get slightly higher fps. 

What I didn't know, was that the new machine would constantly throttle performance at regular intervals while gaming. I'm not an expert when it comes to CPU/GPU specifics, but I do know that my old machine did not throttle performance and that my new machine does. The main game im trying to play is guild wars 2. I played both the beta and the actual game on my old machine before returning it to Dell and it never throttled performance whereas the new machine will drop the FPS by 20-25 every 5 minutes or so. I have tried putting the settings on the lowest possible and reduced the resolution to the minimum and it still throttles at regular intervals. This is unacceptable in my eyes as gaming is one of the reasons i bought the computer to begin with and my original machine had no such problem.

I need some advice from anyone who knows a good amount about how GPU's and CPU's work. I have monitored the temp on my GPU and noticed that everytime the FPS dropped, it happened right after the GPU reached 70C. Is this normal? The research that I did led me to believe that 70C is not all that hot and that my GPU could easily handle 85C. I have not monitored my CPU closely, although i do not suspect it is the issue as I had to tone down other settings in other games as well recently. Another possible problem I have come across is that the new computer does not have as good of ventilation, because it is slimmer and has less vent room. All in all I just need some advice as to a possible fix for this. I have updated drivers multiple times, changed settings in Nvidia control panel, tweaked a BIOS setting, and at this point i'm out of ideas and so is Dell tech support. The solution they have proposed is having a technician come and replace my GPU with a GT630M w/ 2GB vRAM. 

My concerns about replacing the video card is that the system will be taken apart and put back together with a new motherboard and GPU. Replacing the motherboard takes a lot of time and many screws and components need to be carefully accounted for. More importantly I have looked all over the internent trying to find a GT630M chip that has 2GB vRAM -AND- is GDDR5, and I have had no such luck. It seems like if the new chip is just going to have ddr3 vRAM that it might not be an upgrade but rather just a different card. Again, I could use some help here as I don't know much in this area. 

I know this is a lot to read and any help would greatly be appreciated. 

Note: I know that mobile GPU's can't really do much with over 1GB memory, the one exception being if using 1080 resolution, which my new computer does have. Also here is a link to my previous thread, which details the extensive  process it took for me to get my L502X replaced:

 http://en.community.dell.com/owners-club/xps/f/3681/t/19456012.aspx