The problem is, there isn't a center at 30 who can step in and help right away. As a matter of fact, I am not sure there's a center in the entire draft that's ready to contribute to a contending team. Which makes getting us a C through the FA market a no-brainer.
Giddens and Walker, OTOH come to a perfect situation where we're not extremely deep, young, or athletic at the swingman position -- but where one of them will be able to get some minutes with another experienced wing on the floor. Let's face it, Tony Allen is the only SG/SF we have under 30, and that's not much at all.
The thing is, at both PG and C we have adequate options. House, Cassell, Pollard and PJ will not blow your mind away, but can contribute positively. At least 2 of the said 4 can be brought back.
Tony Allen? Not so much. We've seen him go from a solid rotation player to a non-factor in less than half a season, and paradoxically he's been getting worse rather than getting better as the season progressed and he supposedly recovered from injury.
This is not to say that we should scrap Tony immediately, but I think there is space on this roster for at least Giddens to make some noise in the regular season. Especially if he's going to play solid defense.