7006s only have 4" mids and an 8" sub; they are the my least favorite Definitive's I've heard and aren't very capable with such small drivers. You could find BP8's or BP10s for $300 or less that I would much rather have. If you get lucky you could find BP20s or BP30s which are of the best Definitive towers.
Do you have a decent sub now? If so, then I would no doubt go with BP8/10/20/30. If not, you could go audition them at least. It will have more bass than the non-powered towers, they just didn't have the best sound quality in the showroom I've heard them in at least. $300 wouldn't be a bad price for them either if you like them. If you like how they sound though and don't have a sub, I would say go for it.