With dram, in most cases you gain really nothing when sub zero, completely independent on how much money you spend.

Define "doesn't benefit". ;) If you don't keep GDDR3 cool on modern cards it simply burns out faster during normal use. Seems to be a common enough issue with the first G80 cards, the 320MB & 640MB GTS, and 768MB GTX. Was a major issue with the 79xx series.

my 320mb is still working no problem, what issue's are you referring to?

Referring to when the GDDR3 starts to fail on you forcing you to underclock it to avoid artifacts and crashes... more commonly affects GDDR3 than the GPU core; in my humble opinion it is the first part of the GPU to typically go bad ingoring the fan. This is based on watching or helping out in several NVIDIA support forums and typically seeing screenshots of GPU Memory caused artifacts or descriptions thereof.

My Foxconn 320mb is so far gone I still can detect errors or sometimes force crashes by running any GPU stress tool, even after underclocking the GDDR3 memory to 700MHz base rate (as low as EVGA Precision allows). Used to work fine at stock memory speeds, but by almost two years I had to begin clocking lower to regain stability. Now the card is not stable at any speeds.