The 760 has a higher multiplier so it can theoretically get higher clock speeds or at least the same speed at lower voltage than the 750. I think it's worth the $15. Only reason not to get the "newer version" is if they have unlocked multipliers, like the Phenom II x4 BE series, or if the price is much higher than the other one like i7 950 vs i7 960.
If you want to save $17, dont get the dvd burner. If you think about it, how often do you really use it? Share one on another computer through the network if you need it or use a usb one. Only time I've ever used my DVD drive was installing drivers.
AUS prices are far different than what is available on newegg, and as I understand they don't ship to australia.
Why not the i3? This is entirely gaming based PC, and from the stats i've looked at; the only difference between an overclocked i3 and a stock i5 750 is a couple of frames, which as its already 30+ does not bother me.
In general, a i3-530 @3.0 can drive any game at 1920 x 1200 well.
Yes, the i3 is dual core plus hyperthreading vs. the i5-750 4 cores. But, very few games need three or more cores.
Here is an article that addresses the issue exactly: http://www.tomshardware.com/reviews/core-i3-gaming,2588...
Spend your money on the best graphics card you feel comfortable paying for.
At your resolution, I would plan on a single very good card. Something like the GTX470 or 6870. If you ever need to upgrade, there will be much stronger single cards available, like the 6970 or GTX580. Your upgrade path would be to sell the current card and replace it with the next best thing.
The advantage of avoiding sli/crossfire is a reduction in up front preparation costs. You will not need a more expensive motherboard with dual pci-e slots, let alone dual x16 slots. You can use a smaller psu of 650w or so, instead of getting a 750 or 850w unit. You will also need less cooling in your case.
Go ahead and get a P55 based motherboard. Consider the merits of a mini-itx board. It will only have a single pci-e x16 slot, but it is tiny, allowing you to install it in a truly portable case. There are many out there. Here is a lian li aluminum pc-q08b case which can hold graphics cards up to 11.8" long. It has great ventilation, and takes a standard ATX psu. http://www.newegg.com/Product/Product.aspx?Item=N82E168...
For gaming only, and little multitasking, 4gb is all you need. Get the cheapest 4gb ram kit you can find that is supported by your motherboard. The i3-series is insensitive to ram speeds or timings. At issue is perhaps 1-3fps. Not worth spending much extra on.