From what I have heard (no first hand experience on 1.9 and therefore happy to be contradicted) the gearbox on the 1.9 will be your issue.
There are 2.4 cars that have that sort of power however you are likely to need updated turbo, larger fmic and possibly water/meth injection.
Will also be dependant on which remap you have and who you can get to custom it once you have added all the hardware.
If you are desperate for that sort of power output it is likely to be cheaper to change the car.
To reach 280bhp, you'd need a big turbo, a big set of injectors, probably the fuel pump from the 2.4JTD, EGT removal, swirl flap removal, uprated clutch, improved air intake and exhaust flow.
Very few get near that figure and those that claim to tend not to give any road wheel figures which makes it questionable.
If you do want to try, you'll be wanting a GTB2260 ideally, a set of 341 injectors (Ducati) or an uprated set of injectors capable of at least 20% more flow, a 4.0 bar TMAP sensor, the 80 or 90mm MAF would be sensible, a clutch capable of 550-600NM and a good mapper.