I attribute the biggest gains in the quality of my home-brewing to the immersion wort chiller.
Adding a wort chiller to my home brewing setup was an easy decision. The simplicity of cooling the wort right on the stove and then moving it directly into a fermenter is a lot easier than lugging a full kettle around. By installing this dual threaded faucet adaptor in my sink, I can both fill my kettle and run the chiller with ease.
In addition to the back saving goodness the wort chiller provides, it also seems to have helped the beer a lot. I mean a lot. Getting a very fast cold break really helps your wort dump the proteins that create chill haze and or turn into off flavors. You can watch them forming as the wort cools! Since I've started using the chiller my beer is consistently clearer and more palatable.
If you want to you can head to a hardware store with the picture above and buy the parts for likely, slightly less than ordering one online.