Mostly haswell release or newer generation are using DDR3-L which means it's not the previous DDR3 with 1.5V but instead 1.35V. And of course almost all company that produce rams have already produced rams for 1.35V

edit: i just saw horns gave you enough info on that just wondering why do you need performance ram? it's costly compared to normal ram and doesn't give you much or have that any difference unless you are OC enthusiasts or work around RAM most of the time. If it's for gaming only it won't be worth, save it for something else 

holloway is right, there is not much apparent improvements in performance if you just swap ram. i have tested and compared them.

for a g750 the best and right investment to make the laptop much more responsive is ssd. usually consumer grade ssd's like samsung 840 evo, and plextor m5s should work well enough for you. if you want more kicks, i suggest samsung 840 pro or plextor m5pro xtreme.

i also suggest you get at least 240gb capacity.

It will improve alot! it's one of the things you will want to have in your gaming laptop.

horns again have list out for you the best option of SSD

Upgrade RAM (just take the normal ram) saves alot RM200(approx) 8gb per piece (make sure you take known brands such as kingston, crucial, mushkin etc etc).

SSD might be around MYR400 - MYR1000 ++++ depends on size

does it occur at home? usually when at kopitiam or starbucks or mcd will have frequent disconnect since there are too many people trying to connect at the same time (congested~ thus like road will accident~)

If you still have this at home alone or nobody connected to that same wifi and still disconnect do try to update your driver to the latest version, or downgrade depends on which is stable . Other than that do check your anti-virus (internet security) sometimes they tend to mess with the connection (firewall option bla3)

If still happen also, go get new wifi card it's affordable (get the one with .ac option~)

it depends if you ask SC to do it. No warranty won't void (usually) or if you do it yourself (by not tearing of the void sticker) won't void your warranty as well. Just remember to switch back to the original card just case when going to SC

p/s: warranty sticker for G55 is located at one of the screws to GPU/CPU. Not sure on G750

2 years warranty. Sound pecah as in only some song or every song/movie/youtube videos?

does it shows the same symptom with headphone plug into the headphone jack?
If not the same, then ur speaker could be busted sort of, send it for warranty then.