Ignoring agorabasta's DRO+ setting which can do nothing but harm, I quickly tried setting Zone -1 (the strongest and only exposure increasing zone setting possible) with Brightness -2 and -1 (-2 does seem to compensate correctly for Zone -1, by bringing the lighter tones back down to normal) and +2 sharpness and High NR. I have only examined the A900 files on screen, but after seeing the effect, I also used OFF, Low, and Normal NR and -3, 0, +1, and +3 sharpness.
He's actually right - +2 sharpness is the first step which changes the grain pattern of the noise from big colour blobs to a tight pattern more like ACR development of raw. If you set -3 sharpness, the noise explodes into big clouds of soft colour and detail is obliterated. At 0 sharpness, it is typical Sony - heavy chroma noise remaining, softened detail. But when you increase sharpness on the A900 (and presumably the A700, which he was basing this on) the noise grain progressively tightens up to resemble Nikon noise more. Altering the NR setting also has its effect, with Low being a good choice, High coarsening the pattern and producing more random salt and pepper pixels.
For whatever reason (and DRO+ certainly is not part of it!) the -1 Zone and -2 Brightness - which kind of cancel each other out, because -2 Zone is a bit like +2 Brightness but gives extra exposure (Brightness changes the gain-curve instead) does work. Folk on dPreview reckon that Zone -1 causes a 0.5 stop actual increase in exposure (settings) and I can confirm that, although agorabasta denies it. So you might get the same result by just setting +0.5 over-ride plus Brightness -2. I tried that, and a few similar combinations, but on visual inspection at 19X mag concluded that the Zone -1 must kick in some extra chroma NR (perhaps to compensate for a curve which opens up shadows, in addition to the extra exposure?).
I agree with Sonolta, I would not abandon raw shooting just because some complex messing around with settings can improve a JPEG (but really turn ISO 6400 into ISO 4500, relatively). Also, if you do these settings, they remain set until cancelled or you pick a different Creative Style - and they even return when you go back to the Creative Style you adjusted. For me that's dangerous, I am good at leaving settings in place accidentally. Making an Memory position preset seems the only safe way, but my M positions are already occupied.