as title i left a message on cr turbo,s facebook page asking for a turbo to get my car to 600hp

my engine spec is

Current spec is : 200 block, cooper rings with six long studs, Carillo h-section rods, Cosworth forged and pocketed pistons, BD16 Inlet, BD14 Exhaust, WRC spec big port head, custom plenum and a good old T4. Running on a L8 with MSD coil pack conversion and closed loop with air to air boost control.it also has ALS&launch control.

my original thought was put a roller bearing conversion on my t4 with a bigger exhaust housing & a gt35 compressor wheel & housing

i was surprised by what cr turbo recommended which is this

http://www.ebay.co.uk/itm/Garrett-T0...#ht_1858wt_700
which is a 750hp turbo

so what is your opinions are they right ?