I'd recomend the T-25. They are easily upgraded, as TE72 said the T-2x series turbo's have interchangeable turbine housings, a T-3 comp cover can fit on with an adapter ring and all T-3 comp wheels can be fitted. I have a T-25 from a CA-18DET on my mazda 323 (BF DOHC TURBO), it starts making boost around 1800rpm and full boost comes in around 3000rpm. The Cordia TC-06 is old skool tech like the CT-20's off 3T's, the best part about them is the comp cover, easily interchanged with other mitsi turbos. Just my 2c.