a good few grand mate unless ya can build it yourself..i wud 100% advise that you firstly upgrade all handling mods...ule need bigger brakes thats a must with that much power and an uprated clutch...and i would get coilovers too. then ya got things like ARB's etc there a lot of traders on here that are very very good and can supply all these bits and bobs.
engine wise for 280 odd bhp ule need a full rebuild of ur engine with forged pistons and rods, metal headgasket, engine mounts, engine management, etc, and sum1 to map it who knows what they doing. i cud well of forgot sum stuff lol
then for 280 id say a td04 turbo kit shud do the trick just lol but it wud be pushed to its limits i think. a td05 wud do it piss easy tho. theres millions of things u can do lol headwork, cams, nitrous lol skys the limit mate :drive:
edit: but u wud have one awesome ride bro!