Agree with some of what Jordy has said, however for a basic office and web browsing PC you do not need an i7, an
i3 540 would be fine and its a lot cheaper.
Also you don't need an SSD unless you want superfast speeds but they dont come cheap at about £1.50+ per GB compared to about 3p per GB on a standard HDD. A standard HDD will boot in a fair time if you dont enable lots of startup programs and maybe opt for a 7200rpm HDD over an 5400rpm HDD.
Graphics wise you don't need much, I play the latest games on a GT 240 without a problem but now you can get some 400 series cards at around the same price.
Like Jordy said, you don't need 6GB of RAM. Stick with 3GB 1600Mhz and then go with the 32-bit OS. Also yes a quad-core processor wont give you 4x the processing power, its more around 3x and similiarly a dual core will give around 1.75x the speed of a single core.