May want to look into setting the card to the reference clocks to see if it improves...just to rule that out. So many are overclocked out the box. Base clocks are 1.75GHz on the memory (7Ghz effective) and 1050 base on the core (boost 1178).

Also may be worth looking at your PSU if you didn't upgrade that when upgrading the card or it has a lot of age on it. The reference design consumes right at 150w on it's own under normal conditions--can get up near 200W depending on configuration and load. Stack on the 45-95W your CPU may be eating (maybe more depending on model and clock), fans, drives, memory, everything else on the motherboard and USB devices and such...and you could easily be in the 400+ range before you know it. Even nvidia recommends a minimum of 500W of reliable power for the system.