Just a small opposite of me...
Well...for me is missing the rich blacks. On the end you almost lost all shadows. If you have a lot light on the scene ( you have an big windows), than you have to get much rich shadows. Because this light is strong for me...and... The floor to overexposed (for what ?) and you missied to correcting the shadows. On the first pic you have shadows under the table, but the final, almost all lost.
Maybe I'm wrong, but I think you have to strech the lights and the shadows (white and blacks) more widely... Just always check the histogram...And on the Camera Raw, use the white and blacks's clamp options. Is there on the corners of the histogram. This is good way to avoid the flat renders.
Keymaster have right, you try to achieve the final render with correct exposure. That's more valuable. Just equalize the cam's setup with your lights intensity. If you have brigter light, than this one, that's good...Than you render should be underexposed with 2-3 stops.
When you feel the HDRI goin' to "rainbow" ( if you have full HDRI ), just use some color correction on it, and If you want to use the background in render, than just put the background in light material and use like the lighting, make color correction and equalize with the other lights and exposure...Playing...you know !? ;)