Definitely try the 970's analog bass management, as it may be just what you need.
What worries me most is that I'm not sure if the correction needs to be made at the pre/pro or at the player. Also, if you upgrade your pre/pro now, odds are that it will be to a unit with HDMI v1.1 or higher support, and in that case you wouldn't be using the analog outputs anyway...

I'd be curious about one thing: what happens if you set all speakers large in the XA2, disable the subwoofer in the XA2, and use the 970's analog bass management. If the XA2 is doing its job properly, test tones of the LFE channel should be able to level-match with other channels in this scenario. If they don't, I'd look to the XA2 - not the 970 or any other pre/pro - for the underlying problem.