La mejor versión de la 5770 sin duda, vale la pena gastarse ese dinero. Para hacerle OC te vale con los drivers que trae la grafica en si Saludos

man the team is always improvable and the one you put is somewhat weak currently

but for what you say about simultaneous videos and other things an AMD-ATI graphic and minimum 4Gb of memory
is the most recommended,
the best thing is that you say how much money you can spend and where you would buy the parts
and so it will be easier to help you

regards

tu sabras cuanto te urge tenerlo ya, pero esperar para comprar componentes mejores merece la pena