For gaming, price vs performance, core 2 duo is better than i7. You don't buy i7 purely for gaming, it's for number crunching, benchmarks etc. If you have the money for i7 then why not, but for a lot less you can get a fast intel dual core or AMD tri core, which both will perform to the same levels as i7.
Obviously i7 is a lot more future proof than the older generations, but at the moment hardware is ahead of gaming (crysis being an exception), so say for example my overclocked E8400 will last a good few years, by which time i7 will be cheaper and mainstream. So by buying 'older' tech, you won't exactly be buying a PC that will only last a year.
So basically i7 will cost you more for the same performance (in gaming anyway), but will have a more future proof system. So again, if you're willing to spend the extra on i7 then go for it.
The GTX260 shown is the older version (192 sp as appose to the newer 216 sp), it's a little bit slower, not by much though. For the price it's a great performer, the 216sp or the 1gb 4870 will be slightly better cards, but obviously cost more.
550W will be enough, im not sure on the antec basiq though. As it's not always about the power stated, it's about what it actually puts out and the power on the 12V rails, also the efficiency of the PSU. Good, reliable makes to go for would be corsair, be quiet, zalman and a cheaper alternative being coolermaster. Any one of these above 500W will be more than enough.