Triple chanel memory on the i7's needs 3 sticks of ram to work, so either 3x1gb or 3x2gb is what you should go for to get optimal memory bandwidth. Intel mobo's do not give you the overclocking bios options that make the i7 so good (usually, the upper echelon Intel ones might, but the features on those mobo's come standard on much cheaper ones from a third party manufacturer). Get an ASUS P6T Deluxe v2 or Gigabyte GA-EX58-UD5 (or P6T / GA-EX58-UD4P if you can't afford those other ones).
Don't get a sound card until you try out onboard sound, chances are you won't need the sound card since most onboard sound is pretty decent these days.
The GPU/Monitor are closely related things. If you get a higher resolution monitor, then you need a more powerful GPU. If you want to get a GTX 285, then you need to get at least a 1650x1080 res monitor otherwise you will be wasting your money on that GPU.
PSU: Corsair 850tx if you plan to SLI later with 2 GTX 285's, otherwise a Corsair 650tx for just one GPU
Case: This depends on what you like more than anything. Do you want lots of lights and windows to look inside? Do you want it to be quiet? Do you want a simple, sleek, refined look or a flashy look? Here are some good cases to look at, these all have my personal seal of approval for room and excellent cooling:
CoolerMaster Cosmos series
CoolerMaster Haf 932
CoolerMaster 830 Stacker
CoolerMaster Storm Sniper
Logitech always gets my business when it comes to speakers. I have no idea what you want out of them so cannot give a recommendation without more info.
I have no idea what the conversion rate of SGD to USD is so that $2600 figure is useless to me, as well to most of the other users here on the forum I think unless you give us a site to look at to purchase from or a conversion rate to work off of.
Also what exactly is this PC for? Primarily gaming? Video editing? or just an all-around PC?
Its a newer version of that mobo. I don't know if there was an underlying problem with the original or not, but Asus released it fairly soon after they had released the original which makes me think that something on the V1 needed a revision. I honestly can't say I have heard anything about the V2 that is better than the V1, but as this is a long term investment I would want the best possible option. The only physical difference between the two is the removal of SAS ports, which you don't need anyways. The V2 is generally a few bucks cheaper too, so its a better option any way you look at it IMO.