If you are interested in the XD9 and/or XD40, check out the site dedicated to these fine pistols, and their equally excellent predecessor, the HS2000:
http://www.hs2000talk.com/cgi-bin/ubb/ultimatebb.cgi
The group there are very knowledgeable and will help you all you want. I suggest using the site's SEARCH feature; you'll have hours of reading.
I've had three of the HS2000 9mms, and ended up selling them to friends who fell head over heels for the weapon. It was one of the most accurate handguns I've ever fired. Many people compare it to a Glock; it is similar in some respects but far different. The only issue was a batch of substandard extractors in some HS2000s that Springfield is replacing.
Noah