This sounds like a decent ppd for the 7970 and i5 2500k, but you could probably squeeze some more performance out. Make sure to leave a core open for the GPU to use, it still needs some access to CPU functions. Also this will vary on work units, some have high ppd and some a bit lower.

As for the core/memory intensive, this really depends on what the work unit is doing. Providing a good balance would be best, as you can't control with work units you get.