well you have 2 things with a turbo

You can either have a FAT powerband quick spool that tapers off up top. Or a laggy turbo that picks up steam higher in the powerband.

I think a GT28RS would give you the best of both worlds quick spool, but still have room to go uptop.

Honestly for 250whp why not just Supercharge it? Its WAY CHEAPER and easier, its instant power when you hit the gas, etc