A couple of choices then.
Honda - Revvy engine with plenty of knowledge with fitting it to the EXI. Plenty of people already been there and done it so you can get good advise.
1.8T - Nice engine and less revvy. More lazy I would guess compared top the honda. But unknown experience with builds outside Marlin. So basically solving problems together as the build prgresses, contacting Marlin a far bit or discussing with each other.
Cheapest way would be T series Turbo. Plenty of torque and been done as well. But years are catching up with it now as the engine has not been in production for a number of years. But still a cracking engine. At 200 BHP, the car felt very angry, hence me crashing it. Detuning it to about 170BHP, made the car feel more normal and acceptable for normal driving.
Geeze this has started to make me think again. What the hell I'm I doing going for 300ish BHP.
But suppose disconnecting the N75 boost controller, will make the car about I would guess 200BHP.
Along any build, you will probably have an idea of how you would like to do certain things, deviating from the standard build.
What ever the build, it's not going to be a cheap build.