Light and picture are lovely but I think he is too high in the frame.
I don't buy into the thirds thing all the time but having his face at the very top and including his shins doesn't seem to ahve any artistic reason and really hirts the picture, imo.
You can add a bit at the top and recrop to get something that seems to cast a bit more emphasis on his face.
The chair adds zero. The_Traveler's demonstration of the mid-thigh crop makes the image better. I would however crop a bit more off of the lower left corner,so that his hand is the main object in the lower left corner area, and also to give him a bit more "room" on the right hand side, to "look into". The use of the window light is pretty darned good!!! SHows texture and contours very well on the pecs and abs, as well as the low body fat he's got; look at those veins a-poppin! His face is also lighted really well. Excellent job on using the light to work WITH the pose.
That last one looks very "real" except that I think you took a little too much off the top, and his face is a bit too high in the image. Personally, I like Lew's crop a lot. I agree with Derrel that the chair didn't add much. The curtains, however, seem to give more context, and I like having them in better than the second image, which could have been taken with a softbox.