you'd only be feeding them half the power(a piece 500x2vs1000x1) but the w6's will take less power to get going...so probably the w6's, maybe the w7...really depends on install and stuff too though.....
Agreed, I had a 10w7 with the 500/1 and changed to two W3v2's and the w3's were louder and sounded better. But if I only had the room for one sub I'd go with the W7.