HD5770 Power Consumption

Hey guys, I got an hd5770, and a 450w PSU. The PSU has a couple 6-pin ports on it (including one saying it's dedicated to pcie) and the card also has a 6-pin connection. Problem is I don't have a 6-pin to 6-pin cable, so for now I've got it hooked up by using the 6-pin to 2x4-pin cable that came with the card, and plugging each of those into a cable that has 6-pins on one end, and splits into 4 4-pin connections, so 2 are used for the hd5770, one for one of my HDDs and it all gets fed into a single port in the PSU.
My question is does this feed enough power to the gfx card? Does each port in the PSU have a limit to the amount of wattage it can output (in which case using the dedicated port is the best option) or does it not matter?