No personal experience of this but have also been thinking about a Shuttle xpc.
A review of the Shuttle SN41G2 that looks heat, noise, pro - cons, benchmarks, etc. is at tomshardware, click here
Don't be put off by this review Toms Hardware reviews can be a little critical of any minor bad points.
and another about putting together a bare bones Shuttle click here for use in a living room.
PS I've been a long time lerker on PCA, this is my first post. Hope links work :)