All bars have some spring to them. I believe that powerlifters use a thinner bar for deadlifting (better grip on a thinner bar, and more spring... which basically means that you pull on it and then it basically will spring the weights off the floor as it hits a certain point. I have no REAL experience with this, but that is my understanding).

My preference would be a stiffer bar. However, a bar rated to 1000lbs should be more than solid enough. The bar you are using now probably isn't even that good and any step up will be just fine. I have two generic bars and they are absolutely fine. I've used them for olympic lifting with full drops from overhead and they have held up.

Should you ever really be interestedin Olympic lifting, I would suggest checking out the Pendlay bars. http://store.wfwclub.com/bars.html

Obviously the price is a little higher, but they are very nice bars. I purchased one about 4 months ago and it is the pride of my collection Of course I pretty much only use it for Olympic lifts. I will probably look at one of those NYBB power bars later in the fall for my own deadlifts.