The RSS widget is quite tightly tied with the RSS reader application so having two RSS widgets showing different feeds might not be possible (without some serious hacking or installing another RSS reader widget on the device - I am not aware of additional ones though...)

What if you installed StockThis application (http://maemo.org/downloads/product/Maemo5/stockthis/) to follow the stock market news and then have the RSS reader widget on your home screen? Not optimal though as StockThis is an application, not a home screen widget...

Hartti