I think the most economical solution would be to keep what you have now and hold out for a while to see what AMD/ATI & nVidia come up with in the near future.
You can adjust the fan speed using MSI Afterburner to a more desirable noise output level if its annoying you with the current whirling sounds.... I'm sure you're already aware of that, though.
May as well give it a go and OC it, the extra heat wont be so great so I doubt the fan will make so much more noise than it does already.
Also, what games do you currently play?