do all the mods in one go - it'll be cheaper in the long run. Just make sure that you have reserve budget for a clutch and make sure that you get the spec right. Going over 300bhp will mean you need a fuel pump, voltage mod (most of the time) etc. the tuning section wil give you more info
Poweritalia do a range of hybrid turbos that are a direct fit - up to 340 bhp or so.
a word of warning about coilovers - they wont magically transform the hamdling of the car, particularly on the road - on bumpy b roads a lot of them are worse than stock suspension. Look at upgrading the rear anti roll bar as a matter of course. Big improvements can be made by playing about with the alignment as well...