What is your budget?
Y580 can supports up to 16gb ram in win8 pro

Both y580 and g55 fit in your budget.
My suggest would be get y580, use the rest money to upgrade the ram and get a ssd as well to boost the performance, and upgrade to 3 years warranty.
Then it should works like beast.

I did some research previously when I consider both Y580 or G55.

When the time I was doing my research, I found there are something that the G55 does not offer while Y580 offer such features. For example, G55 does not provide Nvidia Optimus technology. And I heard that there are many owners of G55 complaint about there is a heat issue.

You may check for the Lenovo IdeaPad Y580 Review Compare To Asus G55 that I have written on soon after I bought the Y580.

Since you have 4k as your budget, with the lowest spec of Y580, you have additional 1k to upgrade it to be a better potential beast than G55.

In regards of after service, sounds like both also have a bit problem here and there.

So I am betting on which known problem is easier to solved and provide more flexibility.

But I heard the complaints with G55 about the heat was not properly solved and seems like Asus SEA are not doing a proper job in responding towards the complaint. In EU or US, consumer that have reported with the problem get to 1 to 1 exchange according to some tech forumers.

I choose Y580 becos have more rooms to customize as both Y580 and G55 are having identical specs. But G55 having a stricter rules where you can't open the machine to do any upgrade bcos of the sticker. But upgrading ram, adding another optional hard disk or MSATA are all easily and available to upgrade on Y580.

Then top up some money you can get 3 years on-site warranty with Lenovo d. My passed experience with HP on-site warranty are really nice. So I am expecting at least the same level of service.

But for gaming machine, Asus Gaming and Alienware those are more famous lor. I have a tight budget always, so I believe Y580 is the best value for money gear than the G55 lo.

Haha, now you are totally the same shoes where once I am having a difficult decision between the G55 and Y580.

Maybe you need a trick that I used in helping me to make my decision. I used a spreadsheet to do the calculation and finally calculated which one is the more worth going laptop.

Hi guys, anyone mind sharing where can I able to grab Y580 15.6” FHD / i7-3630QM / 4GBRAM / 500G / GTX660M 2G with the cheapest price?

Hi bro, I remember Y580 have MSATA port ready.

Should back up first. If i am not mistaken the windows 7hb version of y580 has a software that you can make a backup dvd just with one click. Needs around 3 dvds to burn.

Hi guys!
after surveying Y580 for few weeks, today i just bought it! pheww!
thanks to all that respond to my previous post regarding review about this beast

just bought y580 with f.o.c headphone and extendend 3yrs warranty.

so now,what i need to do? clean install?

yup. i got dicota backpack.
the headphone has a superb bass. i'm not expecting that.haha. but i got a problem with my headphone mic, it does not functioning well 

what's ur budget? if don't have enough budget, just get the 128GB. people are now on SATA3 and yet you still wanna stick with SATA2. better utilize the SATA3. do you need to install so many things on your ssd? just put OS and apps in your ssd, data keep on the hdd. all downloaded stuff put into hdd. i think intel 180gb can get around rm410.
Agree, get the Win 7 version and upgrade to Win 8 Pro. plus if you having problem with Win 8, you can revert back to Win 7 and might use the Win 8 later in the future.