It's been discontinued, replaced by the new CSi A6. I ordered from Amazon a couple weeks ago, but seems to be sold out now. If you have a Fry's nearby, call and see if they have any stock left.
There is one for sale on e bay right now, also available at hifitrader dot com. But of course, these aren't authorized resellers so you won't have the 5 year warranty. The A6 can be had for $400. If that's out of your budget, your best bet might be to buy the CSi3 for $150, or even a CSi25 ($89 shipped from Polk's ebay store), wait for a deal on the A6, then sell the 3.