Iduno, you have an awful nice WR core there... However, Culpepper is the #2-rated QB (ESPN), while McNair and Stewart are #9 and #10, respectively.
Granted, you have to take any rankings with a grain of salt, but it'd be nice to have a QB that will throw for at least 25 TDs and will run for 10 more. Kordell played a full season and only threw for 14 and ran for 5, while Smith scored 8 TDs. Culpepper also had 14/5 TDs, but he only played about 8 games (from what I can remember, I'm not a big Culpepper fan).
I guess based on past performances and future speculation, I'd make that trade.