So my mobo's back. (Yay!)
And I had arranged everything back into my level 10 gt case. (Yay!)
CPU back in place where it belongs... (Yay!)
New thermal paste and cooler applied. (Yay!)
And no signal to monitor. (Boo!)
It's a Gainward GTX 560ti. I know power's reaching it, as the fan on the card is spinning when I turn the machine on.
I think I've possibly missed something horribly stupid. halp?