opty 146 cooling options

i've settled on buying an opteron 146, but i'm not sure which route to go. i will be OCing (on air). is the retail heatsink/fan ok for overclocking, or will i defintely need to get a better heatsink/fan?

so i guess my options are:

OEM and buy a good heatsink/fan

or

retail and just use the heatsink/fan that comes with

i've OCed a lot of 2400-2600 bartons, but that was like 2 years ago, so i have no idea what the heat situation is on something like an opty 146, nor what kind of heatsinks i should be looking into. also, what about fans? i've overclocked all my past PCs, but one thing i'm trying to get away from is how loud the fans are, since they're cranked to max to keep the chips cool.

money is an issue, as i'm trying to rebuild as cheaply as possible, while giving myself a fairly high end gaming rig (7800 gt, 1 gig corsair XMS, opty 146 on a DFI SLI Lanparty (so i can add another 7800 gt when they come down in price)). so i don't want to spend a ton of money on a heatsink, as it would kind of defeat the purpose of buying a cheaper chip and OCing it by buying an expensive heatsink/fan setup.

anyhow, any help would be appreciated.

I hit close to 2.9 with my opty on stock cooling. It is rather affective. I have a huge HSF now but for a moderate OC with these opty's you really dont need some super huge heat sink. Depends on how high you want to overclock. Probably the most common and most bragged about is the Thermalright XP-90. Here is a link for the cheapest price I can find at a good online retail store:
http://www.frozencpu.com/cpu-tri-13.html
Which this HSF is much cheaper on this site than you find just about anywhere else.. especially Newegg.

You will have to look for a fan which is not included with it. Just choose one with the noise level which you are cool with and puts out the most air flow. If it were me I would buy this one:
http://www.frozencpu.com/fan-89.html

Might be too expensive for you though, not sure what your butget is, but definitely a great HSF!