That is why I look at 4770K.
With reference to your usage pattern, there's vituallly no difference, among the Coe i7 4770K, the Core i5 4570 or the Core i3 4360, as IGP is the same, clocks are rather similar, IPC are the same, and almost no application exploit more than two cores.
And with reference to quietness, there's no way to push the 4770K really fast without getting rid of quietness.
My Dell PC has a noise level around 35dB from where I sit, which is about 2.5ft away. The noise levels of Mac Mini and Mac Pro (from 12 to 15dB) are very interesting to me.
As already said, those raw figures, particularly when they are declared specs, are about -meaningless.
But just for the sake of you curiosity, one of my rigs which is somehow similar to you current Dell, is drowned out by a Seagate GoFlex, tested by SPCR at about 11dB, and I guess that it can be regarded as a typical result of a well built and properly configured system (as you may see, CA_Steve's one have a comparable noise output, while being way more powerful than it).
Eventually, I'd second Steve advice: so, if you don't want to carefully setup your system, or tinkering with parts, and you already have all the necessary softwares, in my humble opinion you may comfortably go along the Mini-way.