question on mixing 2X4 8GBXL & 8GBRL with a X79 sabertooth motherboard

[hclarkjr]

i recently upgraded to a X79 sabertooth board and am using 2 kits of 8GBXL on it right now. i have been looking on ebay and amazon for a matching set at decent price. i thought i found set but mistakenly thought they matched when in fact the other set was 8GBRL. i am not using XMP as the computer would not run right so i just have the ones i am running now set at SPD at 1600MHZ . thanx