B&W 804: Big improvement over 704?

I have owned several paris and still own a pair of 805 Signatures and a pair of Nautilus 804.
Your speakers are definately forward, i would never call them bright or harsh.
They are very easily toned down with cabling or tweaks.
They should be a pretty big improvement over your current speakers.
I would highly recommend them as i would like imaging, detail and accuracy over the opposite any day.
Good luck and have fun.

Budget?

Take this opportunity to explore and audition outside the B&W line so you will be confident with whatever you end up doing. Check out the usual suspects, Von Schweikert, Vandersteen, Devore,...