A3071's are very good, they spooled on my 997 like the stock vtg's.
I would say they are still baby snails though, I ran them with a completely stock 997tt fuel system for a few months until I could be ass'd to drop the engine. I was still achieving good numbers just with 100% meth via aquamist.
I eventually installed 1100cc injectors and have been using them for years until my car has finally come to the operating table again.
Im not sure what the 996 stock fuel system is like though.
One thing I would say, is to go with actual 3071 and not the alpha's, I suffered problems with boost regulation and boost creep due to the internal gates and eventually had to close them off and go external. I now run tial 44 mvr wastegates and they regulate perfectly (and give a nice firework show).
Standard 3071's should be cheaper and should cover the cost of some nice V Band manifolds which will save you money later when you want to upgrade to 35's...
As for intercoolers, I went with the AMS set up, its really great and I think the price has come down a lot since they first launched. The Do88 counterpart looks to be an exact copy, and I don't think there is much price difference between them, also considering the AMS coolers come with a Y pipe.