Just watch out not to mix stuff up and power each piece completely from the same PSU (e.g. Riser + GPU from same PSU, CPU Power + ATX power from same PSU etc.)
While you should power all of the motherboard power plugs (24 pin, 8 pin, and all supplementary) off of one PSU, you do NOT need to power risers and video cards off of the same power supply. You just dont.