Your mobo may suck for it I don't really know, however I used to have 1 gig of Corsair ValueSelect ram. I didn't know much about timings or anything else so I basically left all my timings on auto, and was able to OC to 240 htt with a 1:1 ratio. That means I was up to a cpu clock of 2.64 ghz with the best ratio with my cheap ram all on stock heatsink/fan. It did get a little warm so that was why I bought the TT Big Typhoon. Even if you can't do that with your ram, simply set a divider (it makes little difference in performance with the 3700 san diego whether you have a divider or not) such as 5:6 or if possible 9:10 and then you will be almost assured of being able to get a decent OC even with cheap ram. I do have a really good OCing MOBO, the one in my sig, but even with a crappier one you should still be able to find somewhere to change the HTT and possibly set a memory divider. I would definately say get the 3rd party cooling and OC, it is more than worth it.
I was unlucky, my cpu isn't that great of an OCer. I was only able to get 2.75ghz out of it, 2.8 or 2.85 on a suicide run, and only 2.7 really rock stable. But still even that is ok and with my Big Typhoon my system stays perfectly cool no matter what I run. The only thing that gets even slightly hot in my system now is my 7800GTX which I OCed a bit
but even that isn't too terrible so I am too lazy to buy a 3rd party cooling system for it.
Edit: Also if you OC you will need to find where to change the voltage that you send to your CPU and RAM in your BIOS. You could probably post what exactly you have and someone will have some experience with it to help you OC.