Thats the thing with a ute. Bieng such a small cab,means yo dont need monster setups to good sound and volume, which is handy since you dont usually have much space.

If you want to use a sub with splits, invest in an active sub tube. bazooka make a good unit and for compact bass, its the only way to go. I have an older bazooka sub tube in my ute (extd cab patrol) and its heaps. I run 6 inch splits straight from the deck, and its fine.
My brother also has a bazooka sub tube that he bought 2nd hand about 10 years ago and its still cranks despite bieng significantly abused. His is a passive unit and it has outlived three amps now from memory.