I beleive that BBD is stronger and better at boxing out than Powe. Powe is quicker to go to the ball, however.
Powe and Davis are both 3-4 million-dollar players. Pruitt and Walker are worth the minimum and will be bargains for whichever team picks them up. Giddens isn't worth squat. Tony Allen will be another bargain after they trade him away. They don't miss him on defense nearly as much as KG, but they miss him.
I agree about Powe and Davis (at least based on last year's market...its tough to put a dollar amount on them for next year, since the economy could really influence the market, and cost them some money).
Walker isn't going anywhere though. I believe the C's have him locked up for 4 years, and I expect him to be well more than a minimum player by the time he is a FA again (if he ever makes it to free agency).
Pruitt will be interesting. I think he has some maturing to do, but could be a decent player at some point.
I have been saying forever that Allen will look like a huge bargain on a rebuilding team, because he will be able to put up very nice numbers if he is given the green light...I just don't think he will do it for a good team, since he is not good as a role player, but is not good enough to be a star on a good team. I think he is basically a poor man's Salmons or Wallace (and I think both of them are much better on bad teams than good ones as well). He is going to make some GM look like a genius for at least a while.
With Giddens, it is way too early to know what is going to happen with him. If I had to make a guess at this point, I would agree that he will be out of the league sooner rather than later...but I am not ready to give up on him yet.