I said farewell to Shuttle for a while and built a new system based on Intel's H57 based DH57JG motherboard and Silverstone Sugo SG-06 chassis.
DH57JG doesn't offer any real "performance" features, but still has a rather nice feature list and the Intel boards have usually been pretty stable. SG-06 is not the smallest chassis available, but if offers possibilities for later expansion, if needed (e.g. a separate graphics card).
SG-06 next to SP35P2. SG-06 is about 4 cm shorter than Shuttle P2 both regarding height and depth. Width is about the same.
The chassis and motherboard would allow even for a double-wide graphics card, but currently I am trying to see if I can live with the built-in CPU graphics in i5-660 (as I do not game). There is the slim DVD drive on top and the 2.5" HDD attached to the bottom of the DVD cradle.
In the inside I have got plenty of room, as using a 2.5" HDD enabled me to remove 3.5" HDD cradle completely, which leaves the fan pretty open and enables good airflow. I changed the default 3-pin fan to a 4-pin PWM fan, but otherwise no mods. Speedfan takes care of fan speeds.
The left side of the SG-06 has a rather large vent, which helps with a large video card, but might cause trouble when there is no card. I tackled that risk by covering 3/4 of the large vent on the left with a black plastic sheet taped inside the chassis cover. That prevents air escaping too early and forces it to go towards back of the chassis.
I bought short SATA cables - one 30cm long for HDD and one 20cm long for DVD (just enough). That made the cable management really tidy and makes it to look rather spacey: