No offense. MSP has a very good engine and setup for it time... but Mazda5 has much more potential than MPS.
Mazda5 has brand new and better design engine, Chassis, Suspension, transmission, Brakes, Safety... etc,. The Protege which the MSP based on is an updated, improved version (but not brand new design from ground up) of the 91 Protege. The technology different between the Mazda5 & MSP could be as much as 10 years if is not more.
And FYI, the horsepower differnet between a stock MSP(170) & Mazda5(153) is only 17hp. For both car to reach 270hp mark, I will believe it will cost about the same. I don't think you don't need to upgrade the stock turbo, intercooler and other parts on the MSP to reach that mark.
Does it worth the money to turbo a Mazda5? It is all depended on the person who write the check... Will I trade my 5spd Mazda5 for MSP? Hell No.