Have you considered the Regent? The Assault Refit while it's console is garbage the Torpedo is fantastic (180 Quantum).
It comes with Commander Eng, Lt Eng, Lt.Com Tac, Ens Tac & a Uni Lt.
You could run the Excelsior build but replace the Ens with a Torpedo skill (remember you'll get a quantum that can broardside) or a Beam overload.
The only flaw in your ship design is the lack of a way out of Tractor Beams. Also are you running Marion? If not DEM may not be worth running.
As for the Gal X, try out the Mirror Assault (very cheap to get) and remember the Gal X turns worse and is kind of locked to Phasers (The Phaser Lance).
Owning a T5 ship gets you a 3 module discount on it's Fleet version.
I feel the Normal Assault is better than the Gal X, and every T5 Cruiser is better than the Gal R. Since you have a Klingon you probably don't have a desperate desire for a cloaking device on a fed ship.
I was once DKnight1000, apparently I had taken my own name so now I'm DKnight0001. If I ask you a question it is not an insult but a genuine attempt to understand why. When I insult you I won't be discreet about it, I will be precise and to the point stupid.
I own the excel and you can certainly feel the turn rate difference, as far as the phaser lance goes as a weapon most of the time you can write it off I've been hit broadside with it from an old fleetmate with my excel and took a 1% hull hit(really 100>99 not worth using the damn thing)
One thing to consider is the higher turn rate and lt.com tac allows the use of cannon abilities like CSV2. for STFs plasma single cannons do a hell of a lot of damage with turrets aft, KCB aft for the set bonus.
I do see alot of GalX and Excel. It really depends on play style. No regent, that is the worst Zen ship they made after Gal Retro. THe standard sovie with the right build rocks and Ambassador retro is also good.
Allow me to step back in. I am a huge fan of the Spinal Lance conceptually but I am one step away from committing to purchasing and using the Gal-X due to the requirements using the ship demands (based on Wiki - http://sto.gamepedia.com/Dreadnought_Cruiser). Ultimately, its not my playstyle.
OP, as an option, you could log onto Tribble and play with both to test it yourself. Numbers are just a part of the equation, experience is another. I have experience with the Excelsior and the Sovereign and *I* think the Excelsior is better ... but only by ->.<- that much. So, if the Excelsior beats the Sovvy, then it sure beats the Galaxy (in any form) ... imo.