Heat and Noise

Assuming I go for a four hard disk setup there is a lot of heat to be dissipated from the hard disks and the CPU.

The following can be done to maximize cooling and minimizing noise
1. Use large hiperformance fans - atleast 120mm.
2. Low powered CPU's or underclock a power efficient CPU.
3. Enable power management on the hard disks
4. Don't mount all hard disks if you are not using them in real time.
5. Use onboard graphics card if you need it or get a motherboard without one and plug in a graphics card temporarily.
6. Make sure your setup has thermal sensors for all critical sections
7. Add a intake fan - it is better to have more fans running at slow speed than less fans at max speed.
8. Energy efficient PSU - atleast 85% or more if possible.
9. Green hard disks - they will have lower throughput but then they also conserve power in the long run.

Off the Shelf solutions

Currently the following off the shelf solutions come close to it

1. HP Home Media Server EX485
   
2. Acer Aspire EasyStore Home Server H340
   
3. Lenovo IdeaCenter D400
   

Cases

Primarily two things to consider - motherboard and material

Motherboard - I am aiming for a micro ATX assuming all other requirements can be safely fulfilled without overheating.

Design - preferably a cube design acrylic case though I am not sure I would like to see the innards of my server every day. Definitely nothing fancy with lights and all - the aim is  to consume low power not to add disco lights.

Some MicroATX cases with 120mm fans that I liked are
http://www.rosewill.com/products/s_1140/productDetail.htm
- 4 x 3.5" Internal + 2 x 3.5" External
- 1x 120mm Rear Exhaust Fan,(Option)1x 120mm Front Intake Fan
http://www.coolermaster-usa.com/product.php?product_id=2723
- 2 x 3.5" Internal + 2 x 3.5" External
- one front 12 cm fan and dual rear 8 cm fans

Requirements

Some of the requirements are as follows:

1. Low power requirements - it is supposed to run 24x7
2. Should look decent - we cant hide a print server under the bed especially if it is to be directly connected to a printer
3. Wireless connectivity
4. Headless unit - it is a server after all
5. Failure protection - don't want you to loose your filer after a crash
   
6. Noise - you don't want to hear the fan all day long

Some of the technical requirements I can think of are as follows:

1.  Fan should be quite and software controlled if possible.
2. Motherboard and CPU should allow under-clocking - the current cheapest CPU is way over powered for a file and print server. Also this will mean less work for the Fan.
3. Prefer atleast four hard disk cage with atleast one IDE connector (not mandatory)
4. Onboard Wifi if possible
5. Micro ATX motherboard if possible - atleast a mini ATX if that is not possible