go for a aftermarket management like gotech or omex as its as cheap as getting cossy management done then the turbo choice is endless.

a stage 3 t3 would do the power you want all day long and a t34 would do a lot more and you would save alot of money over a gt series turbo.... and if you are on track where you are always flat out you aint realy got to worry about lag that much.

i know a place you can get a stage3 t3 for around £500 brand new and out right and you can buy gotech for around £700/800 for a whole kit or bolt in the engine and go to jamsport and they will fit and mapp the management all in from around £1300 to £1500 , and thats tow in drive out lol