I have a custom box built box for 2 15" solobaric dual 4 ohm. I have them in a box built by some one on here specificly for my Yukon. Its ported but i dont know to what hertz.. My problem is i had a mtx 1500d running at 4 ohms to power both subs. I got a good deal on two hifonics 1606 so i rewired the subs to run at 2 ohms on each amp. For some reason the mtx was way louder and sounded better. Ive been looking for another 1500d but ive had no luck. What kinda amp can you guys recomend to me that will push these speakers even better than the mtx? ive been looking at the sundown 3000. or if you guys can guide me in the direction on where i can find another one. Thanx