Not a bad card. Asus generally makes good products and this appears to be one of them. The real issue for you to make a solid recommendation is:
What resolution do you plan to game at with this card?
What games are you playing?
What are the specs for your current system?
The HD5770 is a good, middle of the road, GPU, but it can't max out a lot of games out there at high resolutions (=> 1920x1080). You would need to step up to the HD58XX or HD68XX class of GPUs for that level of performance.
Good luck!