Not sure what your league scoring cats and position requirements are, but if hits are in there I would be very hesitant to part with a player like Dustin Brown.
Perhaps further info will change my mind, but as for right now I'd reject all of those offers. Spezza is injury prone, but he's got 90 point upside and the Senators' scoring prowess is on the way up. Wheeler doesn't have Bobby Ryan's name recognition or upside, but he's a great power forward that puts a lot of pucks on net and may end up posting 70-80.
Stewart is intriguing and could have a bounce-back year, but I think you're giving up the best player in all of the trades you listed.
10-team Keeper. Everyone keeps 12 + 1 G + 3 "young keepers" (players with less than 164 NHL games played), and 1G. Points for G (2), A (2), PIM (.2), Hit (.2), Blk (.2) SHP(1), W(4), SO(8) Must dress 4C, 4LW, 4RW, 6D, 2G
C - Crosby, Backstrom, Kuznetsov, Eichel, Johansen
LW - E. Kane, Drouin, Schenn, Miller, Foligno, Zucker
RW - Wheeler, Stone, Lindholm, Oshie, Tolvanen
D - Karlsson, Carlson, Dumba, Nurse, Ceci, Pionk, Larsson, Montour
G - Murray, Quick, Koskinen, Blackwood, Georgiev
Minors - Turcotte, Bouchard, Kaprizov