Depending on how you feel about EVF, the A99 is either a small step above the d610 or a big step in everything except high ISO performance. The EVF is a big difference. The A99 EVF is truly superb. More photographers are being won over by the benefits of the EVF, so it's a big selling point for some. Putting aside the viewfinder and live view modes, the a99 is still a bit better then the d610. Better AF system, faster burst rate, less shutter lag, articulating view screen. The d610 advantage is high ISO. Personally, I think the a99 is a better overall camera, but not necessarily so much better to justify the price difference.
Unless a-mount goes mirrorless, which doesn't appear to be happening immediately, a-mount can't match the a7 for high ISO. The mirror reduces the light, hurting ISO performance. When you stick the a-mount adapter on the a7, you get a99 ISO performance.
Still, the a99 ISO performance is quite good. 3200 can still be nearly flawless. 6400 is very workable. Probably a step below the d610, but quite a bit better then the aps-c SLTs.