First off the first couple turbo guys post should just be deleted as they're just wrong and a waste of space. A fp green will spool just as fast as a 20g I know I used to own a fp green. Anyway this is something I'm not new at is turbo selecting as I went threw about 5 with my tsi before I got rid of it. These are the key things you need to look at
1. When you want to hit full boost: A turbo that wil promote traction qnd yet still not be laggy will hit full boost(in 3rd gaer) around 4200rpms.
2. The efficency of a turbo: You can only run 26psi max so you don't want a turbo that only really shines with like 30 psi as you will not get what your looking for even if the turbo is rated to 6-700hp.
3. Even though it kinda falls in place with the first what kinda hot side you want to use(bolt on mitsu,t3,t4?) Choosing a hotside is just as important as the turbo itself. Choosing a 20g with a true t3 hotside will perform diffrent than a 20g with a bolt on mitsu .48ar hotside.
WIth all that said I would look into a gt35r with a bolt on housing. It usualy hit's full boost on a 7:8:1 4g63 at about 42-4500rpms and is rated to like 600whp. It's dual bb so it won't be a turd on the street and at 25psi it should shine just fine.
Edit: keep in mind with that you would have to get a new flange welded on to your dp as you probably have a 5 bolt flange on there now with your cheap ebay get up.