Hmm, that 7200 RPM HD shouldn't be generating that much more heat to rev the fan full blast. Are you sure the HD sensor and cable is solid?

Unless the SSD integration is causing it, but those are supposed to run cooler. If the computer is sleeping and you wake it do the fans come on soon after waking? The HD should take quite a while to build up enough heat to rev the fans is what I'm getting at.

What does Temperature Monitor say.

http://www.bresink.com/osx/TemperatureMonitor.html