is this case tall enough?

I am interested in purchasing a really small case for my HTPC. This HTPC will only be used for streaming my media and light web browsing (no gaming, no encoding, no transcoding, etc). My intent is to use an all-in-one processor like the Sandy Bridge i3-2100. The case I am thinking about getting is 55mm tall. Is this enough height for the mobo + cooling fan?

cant say like that but you can always get an aftermarket low profile cooler

the stock heatsink is about 45mm tall from base to the top of the fan. It should be fine in your case, assuming that is 55mm of clearance and not 55mm of total height as factoring airflow, risers, and cabling may make it too tight of a fit. But as eskro notes, there are a few low profile aftermarket options. The TT slim X3 is 36mm base to fan, and 20-27db operation.

But I have no problem using the 2100T with stock heatsink in a M350

*edit*
ok the heatsink I measured was one I believe came with a 2600K but I may be wrong. I just measured the stock one that came with my 2100T and it is actually 30mm base to fan.