What would be the import duty for a $4000 stereo including speakers,
if I imported it from IceLand via air to New York City?  How would i
pay for it?

Hi there!

According to the Trade Information Center, you need to contact the US
Customs Office to get the specific information you seek:

"How can I get information on import duties and taxes for products
coming into the United States?

To obtain U.S. tariff rates for specific imported products, to check
on regulations such as import quotas, or for general import
information, contact the US Customs office nearest you or call
1-877-287-8667 (outside Washington D.C. only)."

How to Get U.S. Import Duty Information
http://www.trade.gov/td/tic/tariff/import_duties.htm

It is supposedly possible to get these rates online via a searchable
database.  Searching on "stereo" turns up "stereoscopic microscopes". 
I suspect Customs has stereo systems oddly classified, but here is the
database anyway if you're curious:

U.S. International Trade Commission -- 2002 Tariff Database
http://dataweb.usitc.gov/scripts/tariff2002.asp

To contact the U.S. Customs office nearest you, you can look up the
address and phone number for your area here:

Office Locations
http://www.customs.ustreas.gov/top/office.htm

Select Special Agents-In-Charge/Resident Agents-In-Charge

The direct link is here:

Special Agents In Charge
http://www.customs.ustreas.gov/location/sac/index.htm

Customs will want you to be very specific about the item you're
importing, and will likely ask for the name of the manufacturer, a
serial number, and the price paid for the system.

Good luck!

--Missy

Search terms: [ "import duty" ]

I worked in the shipping business for 3 years, I found that often
times it ended up being more expensive to pay the customs fees and
shipping price then it would have been to purchase the unit in the US.
 For example, I know there were some units from mexico that were
charged a %10,000 duty in certin cases.  I know it was not exactly
what you asked, but it was just a comment.....