Assuming each stick is sold separately and not in kits of two sticks, the SDRAM organization appears to be compatible for the 4GB sticks. It would also be better to use the 4GB sticks alone because the memory will work in dual channel mode which is better for performance. Page 16 of the technical document (linked below) indicates that dual channel mode is enabled when the installed memory capacities of both channels are equal.
Unfortunately the Intel® document does not show the information for a single 8GB stick. This is, considering the information provided by Transcend is for a single stick, which is the case in the Intel® DP55WB technical product specification. The information was taken from the following links: