Note if you put them in the rear deck you would have to build a box around the sub otherwise it would be a IF, not sure that the E8 is good for that.
what i would do if i was you is get 2 boxes built same specs and all and make them fit on eather side of the pass through. Box of choice would be a Flat response 20hz tuning. Also tbh i would have got the SA8v2 but then again i like bass alot more than you do