Hi thanks brother ,
well the reference 660ti does not support over-volting and hence no overclocking or minimal overclocking .
And most non - reference cards have the same story except some like the MSI power edition , there is also a Zotac card which is rumoured to be a " speed king " .
MSI have added and external electrical/electronic component ( sorry am not so good in electronics ) which allows over-volting and hence overclocking which gives performance = an overclocked reference GTX 670 ( now I dont understand what this means really ) but its supposed to be good.
Harry, the moot point of this release is the fact that it is a 'soft' launch; their are no reference cards provisioned by nVidia but all the cards reviewed are third-party offerings with performance and components specifications on paper equivalent OR exceeding nVidia's paper on the GTX660Ti. The more over-clocked the base edition of the card, the more you pay for it and the lesser you can over-clock the same.
Another thing I noticed is that in almost all over-clocks for the Kepler cards is that they need a lot of voltage tweaking to reach stability and a really substantial over-clock that lifts their performance, not the case with comparable AMD HD79** / 78** series cards who are happy on the stock voltages and can take bumps of upto ~100MHz -->200MHz. This I attribute to the aggressive binning for Boost-clocks on the former and definitely it did not matter a whole lot in the GTX670 / 680 but for a budget series card like the GTX660Ti this is a bummer. They claim it to be a better buy than the GTX670 and HD7950 but in the longer run the elder cards will perform better thanks to the larger and spatially laid memory bandwidth [in GTX670's case] and huger memory buffer [in the AMD's case]. And again the pricing of the GTX660Ti is so horrendous in India, I see no reason to go for it.
About the cabinet and the CPU cooler, what is your total budget for these after all the expenditure of the rest of the build?