The general consensus around here is that in that price range the best sub is the eD A2-300; it will be worth the $50 increase over the Orb sub for sure.
With respect to your 5.0, there are other WAF approved options in your price range, such as:
- Kef 2005 (except I couldn't find one without its sub)
- DefTech, 5 x ProMonitor 800 (if budget allows consider ProMonitor 1000 for fronts)
- NHT, Absolute Zero x 5
- Klipsch, not sure what their small systems are (others will pipe in)