ClearFoundation

Thank you all for your clarification on the TDP issue,
I mentioned this as there acn be a comparison:
ASUS RT-N56 seems to be able to do the same with a much less power consumption.

If I am to build a router at last, the possible hardware could be as below:
CPU : Intel® Celeron® Processor G530T
MB : Intel® Desktop Board DH61DL, this board armed with an Intel® 82579V Gigabit Ethernet Controller
RAM :Some Kingston DDR3 1333 2Gx2
2nd NIC : Intel® Gigabit CT Desktop Adapter
Chassis+PSU : Some 2 in 1 solution
WIreless : Is it possible if I actually use Intel WiFi Link 6XXX Mini Card? This board has the slot.

Any idea on the onboard NIC?
Actually would it make a different for Intel and Realtek?
Thank you.

@easyspot,
TDP still confuses me. I understand the definition, but I cannot reconcile it to the fact that a range of CPU's, say the Athlon X2 3600+ through to the 5400+ with clock speeds from 1.9GHz through to 2.8GHz can have the same TDP. Speed is generally related closely to power. What this indicates is that if you under-clock a 5400+ CPU from 2.9GHz to 1.9GHz it will use considerably less power than the 3600+ processor. As the processors have the same architecture (internal layout, manufacturing process etc) I find this hard to understand.
The main things I did to reduce the overall power draw were to use a 2.5" disk, on-board graphics, no CD-ROM (except when required for installation) and a pico-PSU. One thing with PSU's, even the 80+ efficiency ones, is that their efficiency drops way down at very low power (say 10-20% of max) so a 450W PSU running at 7% wastes quite a lot of power in the overall power draw of the system. I used a 120W pico-PSU just so it could cope with the start-up power, but even that is generally running between 25-30% which is a bit better on the efficiency front.
It is nice to have confirmation that you can get Gb throughput. I am jealous - very.

@nexusN,
There is one thread in this forum you may want to read about the 82579V where the O/P had to install his own driver. The process is pretty straightforward. Tim has precompiled kmod e1000e drivers here and they more recent than those referred to in the post.. It may just be the o/p had a problem with his board and it will be OK for you, but when you install, I'd make sure you had your second NIC installed at the same time to give you a good chance of LAN connectivity. If you don't have any LAN connectivity it is harder to upgrade the drivers.

ClearOS 5.2 is not good for wireless. There are some posts on this forum but you'll need to track down how to configure it. You also need to ensure the wireless module supports master mode so it can be an access point. I believe 6.1 will have better wireless support but it is only in beta at the moment.

Well about TDP... I tried to compare some processors:
A Sempron 64 2500+ (1.4GHz) vs A Sempron 64 3000+ (1.8GHz) same TDP, same manufacturing process, but 3000+ ate more 3-5w at full load.
A Regor x2 240 (2.8GHz) vs A Regor 260 (3.2GHz) also same TDP n manufacturing process, but 260 ate more about 4-8w at full load.
Temperature depends on load. For me, TDP not important, just find as small as manufacturing process (higher speed at lower power n lower temp), then find lite mainboard (for networking purpose u wont use optical audio, HDMI, bluetooth, etc). Disable (at bios setup) all devices that u not using, to release IRQ, address, n sure will decrease power consumption

I'd probably go for a 240e rather than 240 as it has a lower TDP to start for a similar processor power with but otherwise I'm pretty much with you.

I missed your WinSCP comment, but it is not the fastest way to transfer files because there is a big encryption/decryption overhead. For big files you're better off with FTP or Samba, and if you use Samba to Windoze, it is best with a Win7 machine due to a much better TCP/IP stack. I nearly doubled my transfer speed when I went from WinXP to Win7. I'm also hoping Samba 3.6 will improve things again with the smb2 protocol.

Thank you for your information on 82579,
then it will be feasible to do with the new H61 boards.

For CPU, 240e is a lower power CPU, while it doesn't contain the IGP, taking it into account it should not be making great difference from G530 in power consumption, while on processing power G530 does look a bit better.
It would be perfect if there can be a G530T for the purpose, while I don't know why we haven't seen it since 3Q11 it was announced.

For Wireless, I have also gone through some posts in Clear Community as well as pfsense's, it seems wireless is not very mature as a part of x86 router, and there will be much to be done before I can get it working, using the existing router, connecting it to the x86 router, as a portal will be the most painless solution.
Luckily, I have deployed a few 10 Meters Cat 6 cables, so at the moment all my devices are corded and I can leave the wireless adapters later.

For wireless the currently recommended option is to use a WAP or WiFi-Router (cabled to a LAN port with DHCP turned off) as an access point. Hopefully this will improve with 6.1.

About WinSCP, yeah it used alot of cpu resources that's why I use it to see wattage coz WinSCP will force CPU to work at peak load. I also use WinSCP for transfering critical files coz they guarantee no error on transmitting, while FTP n Samba may have error.

About wireless, never use PC to work as wireless coz PC use CISC architecture (eat alot of power, high throughput need fast processor, n of course having more troubles). Better buy branded wireless since they use RISC architecture so you can get better throughput n stability. Consider to buy TP-Link products then load DD-WRT to replace original firmware. TP-Link boards always provide JTAG connection so in case if u make your hardware brick, u can easily reprogram using USB to JTAG.

Note that u can never beat RISC performance since they need less power, lower processor speed, less memory, but having so high performance