Small update as requested ......
received motherboard, CPU and RAM ..... banged them together and put them into a case I had here.
... this is the interesting bit ..... the case is an IBM Netvista which is almost the same dimensions as the Grandia I have on order .... it is a bit deeper but otherwise about the same.
The IBM case has a small PSU ..... about 250/300 watts I think ... and it powered the board without problems.
That case is monstrously heavy though

and the front panel is not quite as nice as the Grandia.
I put a SATA-300 drive into it, booted from USB and installed PCLOS 64bit.
All worked fine ...... but I hit a suspend problem .... not working ..... S2R or S2D.
So I backed it down to the 2.6.38 kernel and have now S2R & S2D working.
Once the 2.6.28 kernel was running I noticed that the CPU is now 'stepping' frequency, which it was not previously, with the 3.2.18 kernel.
M/board
MSI H61MA-E35 (B3) mATX LGA 1155
CPU
Pent Dual Core G630 2.7Ghz
Stock cooler.
At idle the CPU is about 38C, and under load ... playing 1080p video reaches 56C.
Up to nearly 80% CPU use during playback though is not good looking.
I tested with sound out to a pair of USB connected speakers, and did not get a chance to try the HDMI out.
I am a little worried about the sound on the HDMI .... never having used an onboard HDMI I don't know how it should appear (if at all) to the OS.
At the moment there is nothing to indicate any sound channel on the HDMI (in audio controls).
Maybe it switches from internal to HDMI automatically ..... or worst case maybe there is no audio on the HDMI ...... time will tell.
At least I have the suspend situation sorted with the 2.6.38 kernel, which also sorted the frequency stepping situation that I had not noticed prior to installing it.
later

EDIT:
I forgot to say that from the Grub selection page to usable desktop (auto login) takes about 42 secs when using KDE, and approx 22 secs when using LXDE.
Makes me wonder how much of an improvement I will see when I add a SSD drive in place of the SATA 300 ......