looks like you should have about 50mm radius of clearance (to the ram slots)
what ram are you using? does it have tall heatsinks? If yes, you're probably looking at a low profile heatsink with ~92mm fan
what CPU are you using? Many of the smaller low profile fans recommend 65W or lower TDP processors, which mostly limits your options to the ~120mm fans
if it's an i5 4670k, that's an 84W TDP part
http://www.bhphotovideo.com/bnh/con...LTFrMgCFQ86gQodJVsGIw&is=REG&m=Y&A=details&Q=
cnps8900 ~$39: 110mm, so won't work with ram with tall heatspreaders
What kind of budget are you looking at?
http://www.tomshardware.com/reviews/low-profile-heat-sink-mini-itx,3639-19.html
tomshardware's review of 8 low profile hsf
silentpcreview of several low profile coolers
http://www.silentpcreview.com/article1317-page5.html
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if it's within your budget, you might want to look at a CLC w/ 120mm radiator like the corsair h55 ~$60-$10 MIR
http://www.newegg.com/Product/Produ...1029&cm_re=corsair_h55-_-35-181-029-_-Product
these provide performance on par with tower coolers in a more flexible package. An added bonus is that you can jostle your computer around without fear of the tower cooler damaging things :S.
There's not really a great budget option in the low profile segment at the moment. Sometimes they'll go on sale, though the majority of sales are on tower style coolers. If you want something matching the performance of a hyper 212 in a small low profile cooler, you pretty much have to go with a closed loop/AIO cooler