wow this is a silly poll. The Ca18det is an amazing engine and can make a hell of a lot of power for how small and light it is(~280lbs) But is by no means a torque monster engine. Its a small displacement turbo engine. That basically means its the exact opposite of a torque monster. But it rips and it pulls.
If torque is your key to happiness then a big V8 is the only way to go. Anything 5 liters or more with at least 300hp will have more than enough torque. In that list is pretty much: hopped up small block chevy, hopped up small block ford, hopped up ford 5.0, chevy LS1 or any 5.3/5.7/6.0 LSx truck engine.
If you want a import turbo motor AND torque like a pro then you want a Toyota 1JZ/2JZ or a Nissan RB25/26. They're all 6 cyl turbo motors And they all make very sexy vroom noises.
If you want to stay Nissan and stay 4 cyl but you want the torque of the gods then you want a FJ20et. Its the closest any mortal man will get the Nissan racing 4 cyl holiness (the LZ20B). The FJ was a homologated race engine approved for rally use as a 2.4 liter carbed NA motor. In production it was a 2.0 EFI turbo motor that lived in Skylines ans Silvias. Its a beast but living the FJ life takes a special kind of dedication. Not unlike the dedication it takes to be an S12 owner. Just more so.
My advice? What engine you go with depends on what you want to do with the car. Most people just want a swap in their street car. A CA18det is great for that. Its correct to the chassis and is a beautiful and well engineered engine. The SR20det is also a good street engine. They are easier to find through local car scene connections and so are the parts for them. SRs and their parts are wildly more popular and easier to find in comparison to DOHC CA parts.
My first swap? CA18det. I loved that engine and wish very much I still had it.
Good luck.