I purchased from the Dell Outet Store a refurbished Precision T7500.  Single CPU (xeon X5667) with 2 GB of ECC registered Ram, 1333MHz. 

Not sure how that came about because 2 GB is not a supported configuration according to the User Guide.

I will be purchasing from Crucial a 12 GB kit (4 GB x 3), which is a supported configuration.  Same type as the existing 2 GB.

My question is can I keep the 2 GB for a total of 14 GB?

14 GB is not listed as a supported configuration, but then again, neither is the configuration which Dell sold.

Please identify whether your answer is from experiernce or assumption.

Thanks