I agree with much of what you said above and I'd also be looking hard to shop Seabrook before his value deteriorates. For most of the last 3+ seasons he has not played near the level of a 5.8 million dollar a year defensmen. I'm not as up to date on pending UFAs and spend even less time trying to find viable trade partners but I'd at least see what's out there. I'd also throw Sharp out there as well, but more from a feeler perspective. If someone makes a stupendous offer I'd move on it, if not hold on to him. But for me Bolland, Seabrook, and Carcillo should be moved (or bought out/demoted in Carcillo's case) if at all possible.
As to the OP's question I'd take Stalberg and it's not even close. Speed is unparalleled, but he's made profound leaps in defensive aptitude, puck carrying skills, and cycling abilities that really make him an invaluable player. He's still not very good at corralling great passes and turning them into goals, but his shot is also much better than it was when he got here. Not only do I think Stalberg's a better player now, but I also think he can continue to improve moreso than Bickell. He'll be the rare case of a player that enters his prime in his late 20s, and due to his gamebreaking speed, will prolong his prime into his 30s. Right now he's easily a 2nd line talent that can play on all three lines, depending on the personnel (if a team needs a sniper on the top line Vik does not fit the bill).