Yes, good you haven't bought it yet.
Some of the members here have helped me settle on getting the HD 5830. This card is more powerful than the 5770, but because these cards are older now, the price of the 5830 is lower than the 5770. I noticed the link you have is from the US so I'm not sure about the prices there but in the UK the 5770 is about £85-90 and the 5830 is £75.
Also to note, the 5830 has a higher power demand so you need to check your PSU supply.http://www.hwcompare.com/14/radeon-hd-5770-vs-radeon-hd-5830/
Use this website to compare GPUs I find it really helpful.