Heatsink/Motherboard Compatibility?

I'm about to upgrade the AMD 4400+ CPU on my HP Pavilion a6110n, to a AMD Athlon 64 x2 5600+ Windsor 2.8 GHz Dual Core CPU. The jump from 65w to 89w is going to require a much more reliable HSF than the stock cooler. My CPU temps are rather high (around 60c) as it is with the 65w. Price is not really an issue. My only dilemma is that I'm not sure what I am limited to by the size of my motherboard.  My motherboard is a micro ATX Asus M268N-LA Narra.

My current stock HSF seems to be some model from Taisol 12VDC obviously socket AM2 compatible. The fan seems to be about 70mm in diameter.

Once again, price is not an issue and I'm basically looking for something with good airflow, which apparently usually correlates with larger fan. Would it be correct to assume that anything that is socket AM2 compatible will work on my mobo given available space? Many high airflow fans are 120mm. Would it also be safe to assume that this would be too large for any micro ATX mobo?

If I am limited to something like a 70mm fan, ASUS X-Mars 70mm Ball The Light Cooler for Dual-Core CPU has better airflow than any other fan of its size on newegg.

I plan to use Arctic Silver 5.

Thanks for the help!

Is this what the socket looks like?  I'm mainly referring to the plastic bit surrounding it, which will be what holds the cooler on.

If on your board it looks like that, then the next thing i ask is that since you have a micro atx board, then do you have a regular size case or a smaller one?  Either way you need to know how much room you have in the case to accomadate certain coolers.  Or, like you said, you could get a lower profile cooler.  Nothing is too small for a micro atx motherboard, your restrictions lie in what surrounds the socket and also how large the case is.

[edit] Did some more research and it seams that it is a midtower case.  Also, I just thought of this, are you buying the retail version of the cpu?  If so, you will get a cooler with it and it will do just fine.

I have a fairly small case http://www.pricescan.com/ItemImages/ImagesL/184720.jpg

It would seem the stock HSF unit is about 8 cm X 8cm and only half an inch away are RAM slots.

Because of my limitations I am now considering http://www.newegg.com/Product/Product.aspx?Item=N82E16835101028 and

http://www.newegg.com/Product/Product.aspx?Item=N82E16835193002.

These are the 80mm/70mm HSF units with the highest respective airflows.

I personally recommend Zalman coolers for low profile requirements.  However these are pricier, even though you said price does not matter.  The reason I am hesitant about the two Asus is that they will be loud.  You cannot control the speed of the fan and having them running at 3000rpm may be unbearable  (to me it would be.)  The Zalman coolers will set you back $50 and they include free shipping, unlike the Asus line.  Either way, the ASUS and the Zalman will be sufficient at keeping your cpu cool, although the Zalman will definately outperform the ASUS in cooling and be quieter.

[edit]  Also, the 70mm fan ASUS is not compatible with AM2 sockets.  BTW, I'd recommend the Zalman 8700 cooler.

Ah woops, I just realized the compatibility goof.  I really don't care much about noise either.  the top priorites are something that fits, and has high airlflow.  I don't think that Zalman will fit in my case. 120(L) X 123(W) X 67(H)mm.  If you look at the above picture that HSF is a 8cm x cm square.  I would worry even about the 80mm Asus fitting. 

So what are the dimensions of the current cooler.  I automatically assumed that the fan in your computer is 80mm.  Am I wrong?

The square measures around 8cm on each side so i guess it would be safe to say the diameter of the fan is 80mm?  Does that sound accurate for a stock cooler in a micro ATX HP with an AMD X2 4400?  As you can see in the particular Asus I've shown, the fan is 80mm but the heatsink extends a bit beyond on eitherside.  Though it extends at a higher elevation I still fear this may not even fit.

Well, last I checked 8cm is 80mm.  Micro ATX boards are only shrunken down.  This basically means all of the sockets are there, but it lacks some features.  Your ram slots are the same ram slots that would be on a standard ATX board from the time you bought it.  The socket of the cpu is the same am2 socket you would find in todays market, on both the Micro ATX and ATX motherboards.  So basically, you can put the same cooling components on your motherboard as someone does on a standard ATX board.  However, your limitation lies in what case you have and the dimensions.  Given the measurements you gave me, with the 1 in to the top of the case, to the .5 in to the ram slots, I looked at the dimensions of the heatsinks on the market, given the sizes vary greatly. 

That 80mm Asus heatsink should be able to fit in your case, since it is basically the same size as your current cooler.  What I recommend measuring is the distance of the motherboard to the side of the computer.  I say the side because the motherboard usually sits vertically, with the heatsink's fan pointed horizontally.  You want the distance from the motherboard to where the case panel would be.  Hope I explained that easily.  That should give you an idea of how tall of a cooler you can buy.

[edit] Just realized, you can't use the ASUS cooler because it is not AM2 compatible.