Sounds like you have weighed it up quiet well already. What sort of games do you play, do you need fast update for twitch games or do you value eye candy more? Is noise that important?
Looking at the noise graphs on Anandtech, the 295 is indeed loud both idle and on load, but then your current 5870 is probably not exactly ninja stealthy :)
http://www.anandtech.com/show/3809/n...he-200-king/16
I have a simple way of deciding this sort of thing. Take a coin, toss it, and heads you buy the 295. Now that is decided, do you feel disappointed at the outcome?? If you feel gutted at the outcome, then the other card is for you!
Honestly, try it. Tossing a coin doesn't always work, but amazing how often it does :D