you still haven't pulled the trigger yet?
the CF card approach is superior over hdd for several reasons. Less heat. no moving parts, much less battery consumption.
the 671 is also a one box solution. meaning that you plug in mic cables and that's that.
for separates...., there are analog preamps and preamp / AD combo boxes (like the Mme or V3) , and there are small analog based recorders (no digital input) and then there are (few) with digital inputs that would utilize the outboard AD of another product.
IMO..if you want to familiarize yourself w/all the products available, you should cruise the retailer websites and get a feel for whats out there.
get yourself a catalog from fullcompass or sweetwater.
even check out musicians friend.