How much better is that core i7?
See the specs HERE
at Intel.com Read the "Overview" and see the "review and benchmarks"
Here is an independent review of the i7 HERE
All in all, it is faster with a better kind of processing. QPI(Quick Path Interconnect) versus the more known and common FSB(Front Side Bus)
And why is it cheaper then?
You would be surprised at how cheap some of the newer technology can be compared to it's predecessor. For various reasons, marketing, advertising(word of mouth), and sales, providing the newer stuff at a affordable price can actually help make more money in the end and get the public more accustomed to the "new stuff". There is probably about 100 other things that come into play too.
I'm not going to explore all of them.
Also how much better is triple channel ram?
Its not a whole lot better, but the way I would look at it is that is what the i7 board requires and the ram is not going to be any worse, that's for sure. It is faster but not noticeable really. Again, the best way to look at it is that it is not worse. And $20 bucks isn't that big of a deal as long as you are within your means and budget.
Also how come the ram is so cheap?
I guess I have already covered this in a way, but also remember, RAM is cheap anyway. I bought a 1GB stick of PC 2 5300 for my laptop about a month ago for $12. RAM is always the cheapest and most cost efficient way of increasing system performance and speed.
I like the fact that the mobi has 2x PCI 16x 2.0 slots but will I be able to use 2 nvidia cards later on and put it in sli?
NO, a motherboard has to be SLI Certified. This board is not. Just because there are 2 PCI-Express 2.0 slots does not mean you can run SLI. This would just be an excellent extra slot if you wanted to put in a nice sound card for example. The sound card I'm looking into for my build requires a slot like this and is over $200.
With all that said, I want to be honest with you. I have never used the kind of Quad Core processor you are thinking about or the Quad Core i7 that I have now recommended. I just simply can't afford such things right now. So I don't want to come off as telling you all this from actually using the two different processors, I just know what is said and what is on paper. I don't game either, so a Core 2 Duo is all I really need anyhow.
Kamille may be able to offer more insight to this if she is still following the thread. Kamille, you here?
Something to keep in mind also, is that the board supports up to a QPI of 6.4GT/S. The processor I recommend is 4.8GT/S which means that at a later date in time, you could upgrade to a faster i7 once the cost of the 6.5GT/S come down a bit. The only one on newegg is $1000. HAHA.
Hope that helps. And remember, either way FAST, FAST, FAST. I'm jealous