As for the questions. I honestly do not know how Corsair implements the larger versions. They could boost the density a bit more and still only use 8ICs but in all likelihood yes they do use 16ICs. This should make it faster. I will see what i can do on getting a sample. :)
Will people notice a difference between a M4 and the GTX. Yes. It is faster. Will it be large enough to justify the price....hmmm that is not so cut and dry. The M4 is still good kit. Its only 1 gen out of date. My rule of thumb is wait TWO gens before upgrading. If that is not possible...then yes the GTX would be a very good choice.
Compared to a 840. I think the GTX would be a touch faster. Honestly only sticking point is on firmware. I would take a wait and see attitude and see if they sort things out. IF they do and get the speed drop off w/ data sorted out..this drive becomes a 'no brainer'. But LAMD dont have a track record. So wait a firmware, see how it changes things and THEN make a decision. IF this is not possible....take the risk. I think it will pay dividends.
edit:
and for the record....the GTX is
never leaving my hands. I like this drive...a
LOT. I know I would spend money and take the small risk in a heartbeat...and will be in the near future for a couple builds.