So far I have overclocked it to 2.73 ghz (non overclocked 2.50ghz) it was my first time overclocking... Can go any farther (3.00) when im using only the fan that came with the cpu with out the cpu overheating or shutting down?

I have a 500w psu

get a better cpu heatsink and fan before u start. that is a must for over clocking. next go here and read all stickiesin the intel section before asking questions.

http://forums.extremeoverclocking.com/

I am just editing to put another link for u to read

http://forums.extremeoverclocking.com/showthread.php?t=79266

Ive heard of people overclocking it to 4.0 Ghz with stock heatsink, but i would get a better one anyway

You can certainly go up to at least 3.0ghz with stock, no need for voltage boosts either.Intel stock sux, but it can manage because heat increases exponentially in relation to speed, so you can go a decent speed with the stock, but for marginally higher overclocks, you will need an aftermarket.
You can probably go up to 3.5 at least, keep your temps below 60 and voltage below 1.3 - 1.35.

As long as your temps dont go higher then 65 celcius using core temp, you can go as high as you want. I would not go higher then 1.375 vcore with e5200.