Well this is a different subject already...
He is correct about the multipliers, you can overclock either way but have more, better options than a intensionally limited processor.
More on that below-
Psu wont be really affected by an overclock- yes it is doing more and will use more power but tiny amounts compared to the addition of an extra video card or two....
If you really want to do some overclocking then both cpu and cooler are marginal- now when I built current desktop it was the same month my c2d e8400 came out it was roughly 200 bucks- at that time a 3 ghz c2d that was unlocked was at least three times that cost- that was my choice for the standard processor.
By marginal in terms of the processor, I mean not as good or easy- by marginal in terms of cooler I mean good overclock or bad one.
As mentioned above- heat is the enemy- the unlocked processor has a much better chance of not overheating for a given trial-(speed) but the cooler is king of this process- liquid is best but expensive- air cooling is for the rest of us.
I googled and came up with a website all about cooling- when you get into overclocking EVERYTHING is its own subject.......
frostytech tested and made a list with the top 10 coolers-
Top 5 Intel & AMD Heatsinks on Frostytech
now I have had many dealing with thermaltakes b-stock store and they have a frio for 39.99- their shipping is not out of line and I have been quite satisfied with the products.
Welcome to Thermaltake
Another thing to consider is "Will a big a$$ cooler fit both my case and motherboard (meaning will it hit the ram or the northbridge etc..) -" read all the case reviews at new egg and see someone already built your setup. or at least fit the cooler in the case...maybe just google it.
Now for the multiplier- really cant explain it faster than these guys- giving you a link, Got it by googling "how to overclock" you need to do some reading as I really cant explain many of the questions you have (or will have..hehe) so look here-
Overclocking FAQ (Frequently Asked Questions) - How to Overclock! - Overclockers Club
I would add that most overclocking is for hours of fun- some hair pulling and bragging rights. The real change in computing speed is generational and the best overclocker in the world cant make a 486 in a warehouse sized case faster than my laptop----even with liquid nitrogen......
cheers,
Bill