If you aren't going to overclock, you don't need a "K" processor. Depending on budget, you might step down a notch or two from the 2600 and save yourself maybe $100---then use that saved amount somewhere else, such as toward a new monitor or maybe 8 GB of RAM rather than 4 GB. No need to get fancy RAM in that case either--get ordinary stuff that runs at 1.5 volts.
I'd make sure the case had large fan mounts--120mm. That way you can use fairly low speed fans that are virtually inaudible. Good fan brands include Noctua and Scythe. Some are quieter than others, so do your research. Under 1000 rpm, the better ones are all but inaudible.