I think for its price you can for an audioengine A5 presently and add a capable 8 or 10 inch subwoofer down the line.The focal subwoofer has a 6.5 inch driver i would tend to believe one atleast needs a 8 inch driver. The 6.5 inch on the focal might be more to add some bass to their satellites and not a real subwoofer.
I would say go for the audioengines and later down the line add a subwoofer to them and have a full fledged capable system rather than going for satellite & 6.5 inch woofer combination.
I am currently using the audioengine S8 with my audioengines A5 and i listen to mostly psytrance which has a constant bassline. I am quite happy with it. But you can mate them with any subwoofer generally.
Although the focal looks really nice since its meant to complement a mac, i dont think its worth the price even the review said it did not sound all that great.