Overclocking is kind of like driving a sports car. At regular speeds you drive around safely with no problems. Hammer the pedal down and now your really flying. If you plan on overclocking then you plan on driving fast so to speak. Just like a car, you can't just have a fast motor. You need the tires, the brakes, the suspension, the whole package in order to do it SAFELY! There are these same type of factors that will limit your abilites to overclock high and remain safe. Motherboard limits, cpu limits, power supply limits, cooling solutions and ram to name a few. I pretty much agree with your buddy that having fast ram is a necessity in order to go fast, but not all ram is created equal. Just because a manufacturer rates the ram at a certain speed doesnt mean it can't go higher than that speed, especially if it is quality ram. You can buy cheap 4000 that doesn't overclock that well, and buy some quality pc3700 that will go above and beyond what the 4000 is capable of, make sense? So in essence you need the whole package in order to acheive great overclocking. Just buying pc4000 and sticking it in a cheap limited motherboard will defeat the purpose. I think you should focus on CPU and motherboard first. Once you have an idea of what will be achieved with those two elements then determine your ram needs. Have you decided on or purchased a mobo/CPU yet? If not, take your time, don't rush. Saving for a few more days or couple of weeks is alot better off than buying something only to realize you want something else. In short yes pc4000 will probably suit your needs now and in the future. But look at the whole picture because there is definitely more to OC'ing than just ram Personally I don't think Kingmax is that bad, but I would much prefer crucial, OCZ, even Geil makes some nice stuff. Just keep asking questions and read the posts. You will get a better feel for what you really want and need that way.
Best of luck on building your first computer!!
By the way, WELCOME TO THE FORUMS!!!!!