Unger Sorum and Morrow are likely completely out of the question (like Nikishin), since there's a chance one or both could make the roster next year (Sorum especially looked really good in camp/preseason, just not NHL ready yet). Nadeau likely a no-go either right now. This front office doesn't like sacrificing potential long-term players for short-term unless it's someone they've already decided isn't likely part of the future team.
An understandable approach, especially if they don’t think they’re quite ready yet to be truly competitive in the postseason. There comes a time in a team’s competitive window where they have to be willing to sacrifice potential for present value, and Carolina may not be there at this point. But if they want Stamkos he’s the caliber of player that will return a team’s top non-elite prospect(s) as a rental.
Despite what many on this forum unrealistically expect when it comes to their team’s top players potentially being traded with little term remaining, competitive teams looking to add an impact player at the deadline don’t deal core or key complementary players (as they’re needed to help the team win now) or elite prospects (as they’re simply far too valuable in a cap league to give up for a rental.) But quality roster-ready prospects who are non-elite and unproven at the NHL level are dealt all the time at the deadline in these sorts of trades. They are the type of prospect that fans tend to overrate but GMs understand are far from sure things. If I only had a dollar for every time someone on this forum declared such players “untouchable” only to see them fail to make an impact at the NHL level.
If Carolina doesn’t think they’re in a position yet where adding Stamkos would put them over the top then I certainly wouldn’t blame them for choosing not to pursue him. But if they did want to acquire him none of those prospects would realistically be off-limits. Stammer won’t return a proven NHL stud or a sure-thing future star as a rental, as a lot of people on this forum unreasonably expect for their team’s potential deadline sales, but he won’t be dealt for table scraps either.