Hi Ajiramm2,
Welcome to Sony Community!
We don't recommend upgrading the graphics cards because we can't guarantee the outcome of the upgrade. Although, it may be possible to achieve what you mentioned above but Sony does not support or provide assistance for this.
We strongly suggest contacting the Sony offices/Sony representative offices nearest to your place of residence in Asia Pacific region http://www.sony-asia.com/countryselector.html?hpid=countryselector:AsiaPacific. Due to proximity, they are in a better position to respond to your questions or concerns.
Regards,
Jen
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