You can have your current turbo rebuilt and have the compressor modified to flow about 10-15% more air. Since fitting 33" tyres I have started looking at something like this. Like any turbo increase there are trade offs. Usually the bigger you go, the more lag you experience. Hence reducing drivability.
For me it is all about the peak torque curve. Making it fatter, not peaking higher in the rev range as I want more torque in 1500-2000rpm range. This improves off road fuel economy. It's not about saving $2 every 100 km. It's about extending off road range.
With small td dual cabs like ours you can either chase a peak torque value to impress your mates or you can build something that pulls harder from down low and achieve real world performance gains. You will know which one you want. Google Kinugawa turbo. There are a few on newtriton.net that have used them and are happy. Good luck.