Value RAM sticks from any brand - be it Corsair, Transcend, Kingston, etc - will use the cheapest ICs they can source. As such
the ICs being used vary quite often, and their corresponding overclocking capabilities as well.
Someone may get 'X' ICs on his Transcend RAM sticks and hit 1GHz, but there is no guarantee you may get the same 'X' ICs and hit the same overclock.
Premium RAM sticks have a higher probability of using the same IC over much of its lifetime or atleast something similar, which could give a more guaranteed range of overclocks for different batches.
However, I have noticed some of the entry level Corsair XMS2 'Premium' modules usually come with ICs that are not too good for overclocking either. I'm guessing the ones you have mentioned fall under the same category.. if you could get a revision number of these XMS2 sticks, you could have a better idea of the ICs/overclocking capabilities.. otherwise they are really not worth the premium over similar 2Gig sticks.
Wish we could put a figure on how high the Transcend stuff could overclock, but apart from guesses/experiences, there's
NEVER a confirmed figure for overclocks!
However if they are user experiences from a *recent* batch of Transcend sticks, you could make the dive and be just as lucky
You usually need to over-volt sticks a notch for higher overclocks, and thats when they tend to heat up. For mild overclocks, they can stay pretty cool. Again this is not a hard and fast rule, and depends on the ICs being used.
On a side note, I just noticed you are using a generic PSU .. I would strongly advise you not to overclock your system till you get a better PSU
