Check the amount of work to get the rx8 box in.

I love a zetec. There are newer and better engines but a zetec is solid and reliable and still very cheap.

180~200bhp in a zetec is not cheap. If you can live with 150~160bhp its cheap and 150bhp can be done very cheap and can of cause be upgraded as and when funds allow.

For a genuine 200bhp from a zetec will require a fair bit of head work and cams, Or a turbo.
The St170 ( a zetec with as better head) would be a better starting point for a 200bhp na build.

The more you make the less it costs.