The only new part is the 7870.
All the rest were working ok.
When you boot to bios, there is no graphics driver or os involved. Every graphics card has a basic low resolution mode that does not need any driver. Something like 640 x480.
If you see the bad image, it has to be the card or the monitor, and we have excluded the monitor.
One other possibility is a poor power supply.
A GTX650 needs only 450w and one 6 pin pci-e connector.
A 7870 needs 500 and one or two connectors(how many does your card need).
If your psu is of poor quality, it will not deliver the wattage advertised.
Can you test with a known good stronger psu?