That all depends on whether or not you plan to overclock ?
If not, and assuming you have a desktop, minitower, or midtower case, then you could probably get away with it just fine.
If you have a full tower and an AMD based system, and you want to overclock it, no way. You'd need a good HS/F and some additional cooling mods,or your pc will also perform some illegal functions and be shut down.
I work at a major electronics chain as a tech ( I don't want to say which one as many people don't care for us much =) ) and all the athlon systems we sell come with two case fans. They're both usually 80 mm. This is in addition to the PSU fan of course. So I guess if that's enough for all the major PC vendors, it's probably enough for you too since you won't be overclocking. Just monitor your temps. If your case temp gets alot above your ambient temp, it's time to add more case cooling.
Your right in assuming your setup should be ok. You may even be able to do some very mild overclocking if you have or get a good HS/F for your cpu. Are you using Motherboard Monitor to keep an eye on your temps ? If not, get it.
Maybe my computer room is warmer than yours. I have my ac set at 78F (?C). Case temp is at 28-31C (approx. 83 or 84F I think). I have a Volcano II hsf on my 1.2 T-bird (non o/c'd) with Radio Shack thermal compound, and my cpu temp is never under 52C after it's been up and running for a while. I don't understand how you can be using a stock hsf and get such good temps, unless the V2 isn't as good as your stock hsf. I'm using MBM5 to monitor temps. Oh, well. I've ordered AS II, a Delta 7K rpm fan, and an Evercool fan, and they should be here this week. I'll play around a bit and see what my temps look like with various configurations. At least I'm below 60C after playing games for a while (that's the biggest load I put on my computer), so for the most part, I guess I'm doing all right. Like I said, though, I can't help but notice that others here with similar setups get much better cooling results than I do. I really don't get it...
My brain has performed an illegal operation and will be shut down