Temps up to 65c are acceptable but personally I prefer under 50c top end for anything cmos related, cpu or gpu and especially nothbridges (looking at you nv). Anyway your chip is exactly the same as mine - speed / volts and I got approx the same temps with the weedy stock cooler but spent out on a thermaltake big typhoon which is utterly amazing as my chip now idles at 28c and peaks at 41c !, couldnt reccomend this cooler enough as its a down facing fan it also helps cool the nb and ram around it a little. Oh and thats with the 120mm fan set to 50% speed in the bios (msi p35 platinum mobo).
Any aftermarket cooler will do you proud (when you get the cash) with that cpu as its a low power model (approx 50w stock and undervolted less - even overclocked a bit) so if cash is tight go for an arctic cooler - the freezer pro for ex is as easy to fit as the stock cooler and will keep your cpu well under 50c tops and costs as little as £12.
Out of curiosity what will your cpu get up to ?, most of the wolfdale cores hit 4ghz pretty easily with about 1.325v max and some (like mine) will get closer to 4.5ghz !, at those speeds who needs quads !.
What program are you using to measure temperature? Max cpu temp is around 72c, not to be confused with tjunction max of around 100c for the cores. Keep the cores around 70c or below and the cpu temp around 60c or below. If you do that your chip will last longer than you want it to at the voltage level your using.
I use speedfan and yes its the 2 cores temps I read (so far as I know) with the slug temps about 5-7c lower still, my 2nd core always runs about 2c hotter than the 1st but thast quite normal for these cpus.
I should say I keep my case open and never have the side on and have the hdd in a scythe himuro case and the gfx card with a modded vf1000 heatsink as I cant stand noise and if you know the p35 platinum mobo its got the roller coaster mega heatpipe arrangement that doesnt let the power regulators or nb get hot at all, even at 500mhz ish !.
Of course I dust regularly and use arctic silver goop sparingly so Im pleased with my temps and my rigs relative silence.
Back to the op's q tho if hes only getting 50c ish in games with the stock cooler he has nothing to worry about so far as Im concerned and was only pointing out that with even a cheap arctic cooler he would get very good results.
ps speedfan is a good free prog you can google to d/l and if your using it already then dont worry about temps because as long as you dont go above 1.35v on the core (which 45nm dies dont like at all) you will not harm the cpu.