Sidewinder

Since there is the optional rear speaker accessory for the MY 04's, there appears to be a 4-pin plug and play speaker harness under the dash (Step 56). I will be installing Marks S-Pods, and was wondering if I can just tap off of this harness to gain rear wires without using a conversion harness off of the HU. Theoretically, this makes sense, but have yet to see for myself.

Any thoughts or suggestions??