My self-indulgent 2c:
I think NB is fantastic in a US beer (though I have only used German) and adds somewhat of a woody/manly hoppiness rather than a girly fruity hoppiness.
I think that Centennial is a fantastic hop and is very versatile and palatable, I am planning on mixing it with a bunch of target in my next IIPA.
I think that if you are using hops like cascade, use them late and in moderation as per classic examples of style.
I sometimes use chinook, but I use it for the throat-burning resinous grapefruit thing. It is not a mild hop. But, if you find the character agreeable, it is a good, but decidedly loud one.
Below is a IIPA recipe that I currently have on tap. A critic last night said that it is a beer that "requires commitment".
BeerSmith Recipe Printout -
http://www.beersmith.com
Recipe: 48 IIPA
Brewer: Dan
Asst Brewer:
Style: Imperial IPA
TYPE: All Grain
Taste: (35.0)
Recipe Specifications
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Batch Size: 49.00 L
Boil Size: 57.65 L
Estimated OG: 1.081 SG
Estimated Color: 20.5 EBC
Estimated IBU: 111.5 IBU
Brewhouse Efficiency: 75.00 %
Boil Time: 60 Minutes
Ingredients:
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Amount Item Type % or IBU
1.00 kg Extra Light Dry Extract (5.9 EBC) Dry Extract 6.69 %
5.00 kg Pale Malt, Traditional Ale (Joe White) (5.Grain 33.47 %
4.00 kg Pale Malt, Maris Otter (5.9 EBC) Grain 26.77 %
1.00 kg Pilsner (Weyermann) (3.3 EBC) Grain 6.69 %
1.00 kg Wheat Malt, Pale (Weyermann) (3.9 EBC) Grain 6.69 %
0.60 kg Munich II (Weyermann) (16.7 EBC) Grain 4.02 %
0.34 kg Caraaroma (Weyermann) (350.7 EBC) Grain 2.28 %
200.00 gm Northern Brewer [9.00 %] (90 min) Hops 74.5 IBU
50.00 gm Cascade [5.50 %] (Dry Hop 4 days) Hops -
75.00 gm Northdown [9.60 %] (20 min) Hops 16.9 IBU
75.00 gm Chinook [11.40 %] (20 min) Hops 20.0 IBU
100.00 gm Centennial [10.00 %] (Dry Hop 7 days) Hops -
100.00 gm Amarillo Gold [8.60 %] (Dry Hop 7 days) Hops -
1.00 kg Cane (Beet) Sugar (0.0 EBC) Sugar 6.69 %
1.00 kg Corn Sugar (Dextrose) (0.0 EBC) Sugar 6.69 %