Yeah, I don't know if you can hold out longer, but the 8000 series will be here in March, most likely causing another price drop. Otherwise a 7870/7850 is a great choice. Post your specs and it should help clarify if you need a new psu or not.
I also concur that a 7850 is the logical choice for an extra 40 euro (150 euro) or even a 7870 if you can stretch your budget out to around $200 euro's but it all depends on what kinda power supply you have now.
When you get around to finding the label and it's a no name meaning it's a budget unit, I highly recommend buying a good quality PSU. Wattage doesn't really matter you could have a 1000watt PSU but if it's made cheaply it will not output anywhere near that stated amount and most likely cause problems (Blue screens, freezing etc) and or damage parts.
I couldn't see any brand name. However, I'm pretty sure it only have one lead for pci-e maybe i'm wrong. But is there cheap PSU's which could do the job?, I don't mind getting a new one aswell as its not too much (say £30 or below).