700 CC? Are you sure he said that? That might get quite heavy for the back, but if that is truly what you want, then go for it.
Just remember that you will probably need to do some regular work-out with that size, to keep your spine troublefree.
I think Kimber James had 700, by the way, but cannot swear on it.
Anyway, no-one here can really advice you what to choose, as the only one that can tell what you would be truly happy with, is you.