Hi Shaun
Depends on what you want to use the car for a 100HP at the wheels is easy to achieve.
Matts 120y runs a 1270cc,32/36 webber and 104HP and 212nm torque at the wheels(still street drivable)The car has more power now but has not been back on the dyno.
An A15 would be a better way to go as Sidedraught said,cheaper HP.GREG