Right now I'm in the middle of my build with 2 18" BL's with a Trutech Hammer H1 per sub in a 16cuft wall tuned to 30hz.

After this I'm pondering changing to two BTL 18's with a DDZ1.

Just wondering would it be worth it in terms of being a major leap over the BL's and the Hammers ?

you haven't even finished the wall and you're already thinking of a change of setup? Why didn't you just get the BTLs to start with? and what kind of "leap" are you looking for? Perhaps you should finish this install and see if it meets your needs first. At least you'd get a better idea of what you'd want different.

Well the initial aim was to have a crazy loud streetbasser and numbers was my second priority.

However alot of people in the know have said 150 won't be easy to get with the install thats happening now albeit I would have thought so (car is a Ford Fiesta so pretty small)

I didn't get the BTL's as I was told 1.5k isnt enough for them and the BL's are a better option, but I can get a DDZ1 so now I'm pondering getting the BTL's after.

You have two options, choose a loud daily driver or an SPL vehicle...You cannot have both.

You have two options, choose a loud daily driver or an SPL vehicle...You cannot have both.

I don't know if I completely agree with this, but I do understand where you're coming from. 1.5kW will be enough for the BTL. It does give you room to upgrade your amps if you're not happy.

Well the initial aim was to have a crazy loud streetbasser and numbers was my second priority.

However alot of people in the know have said 150 won't be easy to get with the install thats happening now albeit I would have thought so (car is a Ford Fiesta so pretty small)

I didn't get the BTL's as I was told 1.5k isnt enough for them and the BL's are a better option, but I can get a DDZ1 so now I'm pondering getting the BTL's after.

If you build the box a little bigger, 1.5k can and will push the BTLs to its limits.