Wooow! I LOVE this refit! And, I have a couple ideas for you!

1. Lengthen the Nacelle pylons back a bit at the point nearest to the connection with the warp nacelles. That way, it could look a little sleeker and more balanced, imo, than having simply larger nacelles mounted on the original pylons.
2. Torpedo launcher, similar to your Century, mounted right below the deflector dish.
3. MAYBE, just a thought, forgo the impulse engine at the base of the neck entirely, replacing it with an impulse engine on both nacelle pylons, similar to the Intrepid and Vivance.
Just some ideas I thought I'd throw into the mix. Looking really awesome, dude.

Good luck with this project.
-Aeries.
Edit: Thought I'd post some pics, in case you weren't sure of what I meant...