Just to clear up any misunderstanding. A lot of diffrent trade possibilities have been mixed into this thread, so actually Krang was right, because he was refering to trading for KGB.
The rule is that you have to use your "own" pick in order to trade for a tendered player. Tendered players are either Franchise players and restricted FAs. Orlando Pace, Tai Streets, Laveneus Coles, KGB, Darrell Jackson falls into this catogory.
There are no rules with other players. So all this BS (since he's going be to be released anyway) about giving up one of the 1st rounders, that you trade down to, for Seau is actually possible.
Teams can, however, agree on a trade, that eliminates this rule. The Bills were entitled to two 1st rounders, when Atlanta signed WR Price, but came to an agreement with Atlanta, that one was enough. The same goes with Streets. He's is tendered as a 1st rounder, but the 49'ers has stated that they would trade him for a 2nd rounder.