If you are planning on buying an Evo as an existing customer, not eligible for an upgrade(like myself), then I think your best bet is buying from one of the smaller Sprint authorized dealers as opposed to a main Sprint retail store. Where I live there is a big Sprint retailer with a Sprint authorized dealer literally two storefronts away. The official Sprint store told me $449.99 straight up, but the authorized dealer told me he would cut me a break and give it to me at $20.00 over cost + buy my Hero from me for $63.00(which you can do at any Sprint store I believe). He said he would also get me an additional discount on my monthly bill.
Point being, the smaller authorized dealers need the business and will go to greater lengths to make the sale. The larger stores and places like Radio Shack generally have their hands tied and can't really give you a break. I would go to a smaller Sprint store and ask them what they can do before committing to anything, it's worth the try and you might save $50-$100 depending on your situation.