How to print from iPad via WiFi

Hi,

My printer is a HP Photosmart C4680 who's usb cable is connected to a small box or hp print server that connects wirelessly to my Linksys router. I tried Airprint but it didn't work because my printer is not in their list.

Then I tried HP iPrint but this doesn't work either because according to their instructions I have a USB printer that should be connected to an apple airport extreme/express.

So do I get this right, either I buy a new printer that is in the list of supported AirPrint printers

or I buy an apple airport extreme/express, get rid of my hp print server box and linksys router and attach my printer's usb cable to the airport extreme?

Another question is, how is apple airport extreme compared to linksys wrt610n? In other words, what will I loose and what will I gain?

Thanks in advance