Dell Precision M6400 with Ubuntu - GPU replacement?

Hi all you bros,
Ok this is my case. I used dell m6400 (BIOS Dell A13 - T9800 - 8Gb Ram) with Nvidia fx3700m and I really want to be mad with black screen crash.
When I was using Windows, I have to use nvidiaInspector to underclock, this make gaming well and it's not crash when run similar graphics processing (video editing,render), but sometime it still crash. I switched to Ubuntu for work, and I still have to underclock for more stable (not crash). However the frequency of black screen crash seems higher. And I should probably replace this card.
I plan to replace card fx3700 to FirePro m7740 or m7820. However, I use Ubuntu so M7820 is only for linux drivers, M7740 driver is not support from 2012. In fact, these Ati firepro cards were cooler than NVidia quadro fx. But I'm really not sure that M7820 is compatible with M6400? According to this thread (http://forum.notebookreview.com/threads/upgrading-m6400-gpu.676710/), it works fine without modding, but maybe I need more advice.

 

I have the same system but don't often use Linux on it. I would stick with sourcing a FirePro V7740. Since it was the one officially supported by the m6400, there should be less chance of compatibility issues.

 

@lilngu I have already replied to you in the main M6400 thread. The M7820 will work with the M6400, no issues at all. I have the M7820 in my M6400 and no issues there with all the Windows OS I throw at it. However, I am not sure of the Linux side of things.

 

Thank all for reply!
Now this is big problem. Ubuntu was not support for ATI/AMD driver from Ubuntu 16.04. And the best option ATI Firepro M7820 now was bad option. And I gotta find a best solution with Nvidia Quadro Fx . Ok? Fx2700m is less risk but only 512mb, Fx2800m and fx3800m maybe better than 3700m but I dunno is it compatible? 5000M was too difficult to find and expensive. @@
Yay! Hard to solve this case, I think!

 

All graphics cards from the M6500 will work in the M6400. That includes the FX2800M, FX3800M, 5000M and M7820.

The only thing you will notice it causes is the missing Dell logo upon start up of the M6400.

However, all other functions of the M6400 (F2 or F12 function keys at start up) will work and the screen will starting display images when it starts loading the OS.