Billspecfoc, maybe I can give you a little insight. I own a model 8 with choke and I have heard the model 5 on several occasions. The difference between the two isn't minor. The 8 has tremendous bass definition, while the 5 is in no way weak in this area, it isn't able to plumb the depths like the 8. BUT, that's not the biggest difference between the two. IMHO, the biggest gain is the 8's ability to resolve a LOT more detail than the 5. As for whether the 8 could drive your speakers, I'm in agreement with French fries's post. IF you can source an 8, I think it would be a great addition to your system, I know it was to mine.
Good luck with your search.
Good luck with your search.