I have Hamels and Sizemore on my team, if offered that deal I'd take it in a second. I love Kemp this year. While I'm high on Hamels I'm losing faith in Sizemore.
I'm probably in the minority telling you not to do it, that you are paying too much.
Sizemore was injured last year with groin/elbow problems and he still hit 18+ homers and had 13 stolen bases. I can definitely see him hitting 25+ homers and 20+ SB's ( he had 30+ the two years before he got injured)
As a Kemp owner, if offered something similar for Kemp, I'd say no. I'd probably counter with Nolasco and Hamels instead. Sizemore is dead to me.
Kemp's value is at an all time high... #2 on the player rater? (Yahoo) And you're trying to trade two guys who most people would try to "buy low" at this time. If it works out for you, all the better.
You should def do it - Grady's struggling a lot to open the season, Hamels isn't his old self, and Kemp is one of the best players in the league. Great deal for you.