Passat catalytic converter

Hi,

I have to replace 1 possibly 2 catalytic converters in my 2000 Passat V6.
My right cat simply felt down, hanging by a cable.
Mechanics quoted prices between $1000-$1500 per converter, however some web search turns some cats as cheap as $80 (universal cats, also offered by Autozone) or around $350-$400 for passat:

http://www.autopartswarehouse.com/products/products.php?year=2000&make_text=volkswagen&model_text=passat&category=exhaust&subcategory=catalytic_converter

or

http://www.import-catalytic-converter-warehouse.com/epcstartreverse.epc?cookieID=25E1DD17P25E1DD9BC&drillid=7&engineid=V62.82771GASFI@@V6+%2D+2%2E8L+%2D+CC%3A2771+%2D+GAS+%2D+Fuel+Injected+%2D+Non%2DTurbo&clientid=import-catalytic-converter-warehouse

I have 170K miles on my car and hope to keep it for another 80k/3years.

Questions:
1) Under some happy circumstances, could the ‘hanging’ cat simply be reused?
2) Why such a huge difference in cat prices? $80-$1500
Are the $350 cats a decent choice?
For instance this:

http://www.import-catalytic-converter-warehouse.com/item.wws?sku=40464&mfr=EASTERN&cookieID=25E1DD17P25E1DDB8S&drillid=10&clientid=import-catalytic-converter-warehouse&clientid=import-catalytic-converter-warehouse

Thank you