I can't be certain I have exactly the right motherboard, but there
is a picture here of the M2N78-LA. It is branded "Pegatron", which
I believe is an Asus subsidiary. The "M2N78" is an Asus type of part
number (but of course, you'll find no mention of this board on an
Asus support site).
http://h10025.www1.hp.com/ewfrf-JAVA/Doc/images/c01635737.jpg
The first thing I don't like about that motherboard, is it has no
PCI slots. If you wanted to move that high end PCI sound card you own,
over from your old system -- no slot.
The board appears to have built-in graphics, which are fine for
an office system. You'll want a graphics card installed in the x16
slot, for gaming. The power supply in the computer is 300W, which
doesn't leave a lot of room for the power consumption of $600 video cards.
You can get processor benchmarks here. I have no confidence in their
benchmarking skills, but they do have the money to pay people to test
a lot of hardware. I guess that is worth something.
http://www.tomshardware.com/charts/2009-desktop-cpu-charts-update-1/benchmarks,60.html
You could use the Fritz chess game benchmark. Your processor is about
the same as a Q6700 quad core.
http://www.tomshardware.com/charts/2009-desktop-cpu-charts-update-1/Fritz-11,1406.html
The Athlon II X4 630 is a quad core with no L3 cache. Whether that is
an issue, depends on what you're doing with it.
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103704
And yet, when I check a WinRAR benchmark, which historically is a
memory bandwidth dependent benchmark, it doesn't seem to have
suffered too much. It is no longer as fast as the Q6700, and
takes 118 seconds compared to the 92 seconds for the Q6700.
http://www.tomshardware.com/charts/2009-desktop-cpu-charts-update-1/WinRAR-3.9-x64-Beta1,1399.html
In a 95W processor, this would be about the fastest substitute. Looking
in the Tomshardware chart, this gives a WinRAR benchmark of 91 seconds.
So you'd be catching up to the Q6700 again, if you popped this into
the CPU socket. That is, if you frequently did things that benefited
from more cache. Most people don't spend the whole day doing WinRAR,
and as a benchmark, it is intended to highlight a pathological case
of a dependence on memory bandwidth.
AMD Phenom II X4 945, 3000MHz, 4x512KB L2, 6MB L3 95W
http://products.amd.com/en-ca/DesktopCPUDetail.aspx?id=619
Hope that gives you some idea what you're getting.
Paul