The Romulan ship below is from the web site run by Owen E. Oulton. I made a few modifications that make the vessel nearly undefeatable by even a Sovereign-class. In testing the Narada against my Revised Version of the Sovereign-class Enterprise-E from Nemesis in a fight the two ships sustained heavy damage. As for fighting in the 23rd century the weapons would easily out match the versions of the original series and remake constitution-class starships. The constitution-class firing forward phasers on the Narada would not even penetrate the shields, as the shield threshold is high enough to stop the shot without denting the shields.
Environmental Systems
Basic Life Support [12 Power/round] <76>
Reserve Life Support [6 Power/round] <38>
Emergency Life Support (114 emergency shelters) <38>
Gravity [10 Power/round] <19>
Consumable: 3 years worth <57>
Food Replicators [19 Power/round] <19>
Industrial Replicators
Type: network of small Replicators [2 Power/round] <19>
Type: 2 Large unit [2 Power/replicator/round] <6>
Medical Facilities: 5 (+1) [5 Power/round] <25>
Recreation Facilities: 3 [6 Power/round] <24>
Personal Transport: Turbolifts, Jefferies tubes [2 Power/round] <57>
Fire Suppression System [1 Power/round when active] <19>
Cargo hold: 30,000,000 cubic meters <90>
Locations: lower levels of the ship
Escape Pods <13>
Number: 260
Capacity: 4 persons per pod
Propulsion Systems
Warp Drive Nacelles: 5C <65>
Speed: 5.0/8.2/9.1 [1 Power/.2 warp speed]
PIS: Type C (6 hours of Maximum warp) <6>
uprating packages: Package 2 sustainable, package 1 to maximum <6>
Special configuration: Embedded nacelles <76>
Impulse Engine Type: 3 Class 3A (.5c/.75c) [5/7 Power/round] <18 x 3 = 54>
Location:
Reaction Control System (.025c) [2 Power/ round when in use] <19>
Power Systems
Warp Engine Type: 2 Class 12/R (generates 600 Power/round) <130 x 2 = 260>
Locations:
Impulse Engine[s]: 3 Class 3A (generate 28 power/engine/round)
Auxiliary Power: 4 reactors (generate 5 Power/reactor/round) <12>
Emergency Power: Type F (generates 50 Power/round) <50>
EPS: Standard Power flow, +250 Power transfer/round <120>
Standard Usable Power:
Operations systems
Bridge: <95>
2 Computers Core: [5 Power/round] <38 x 2 = 76>
Uprating: Class Alpha (+1) [1 Power/computer round] <4>
ODN <57>
Inertial Damping Field
Main <304>
Strength: 9 [3 Power/round]
Number: 8
Backup <38>
Strength: 5 [2 Power/round]
Number: 4
Attitude Control [5 Power/round] <5>
Communications Systems
Type: Class 5 [2 Power/round] <15>
Strength: 5
Security: -3 (Class Gamma Uprating)
Basic Uprating: Class Alpha (+1)
Emergency Communications: [2 Power/round] <1>
Tractor Beams
2 Emitter: Class Gamma [3 Power/Strength used/round] <9 x 3 = 27>
Accuracy: 4/5/7/10
Lactation: one forward, one aft ventral, one aft dorsal
1 Emitter: Class Alpha [3 Power/Strength used/round] <3>
Accuracy 5/6/8/11
Location: shuttlebay
Transporters
Type: Personnel [6 Power/use] <14 x 6 = 84>
Pads: 8
Emitter/Receiver Array: Personnel Type 4 (30,000 km range)
Energizing/Transition Coils: Class F (strength 6)
Number and location:
Type: Emergency [7 Power/round] <13 x 6 = 78>
Pads: 24
Emitter/Receiver Array: Emergency Type 1 (10,000 km range)
Energizing/Transition Coils: Class F (strength 6)
Number and location:
Type: Cargo [5 Power/round] <12 x 12 = 144>
Emitter/Receiver Array: Cargo Type 3 (40,000 km range)
Pads: 600 kg
Energizing/Transition Coils: Class F (strength 6 )
Number and location:
Cloaking Device: Class 10 [40 Power/class/round] <49>
Security Systems Rating: 1 <4>
Anti-Intruder System: Yes [1 Power/round] <19>
Internal Force Field [1 Power/3 Strength] <19>
Tactical Systems
Disruptor arrays <49 x 8 = 392>
Type
Damage: 240 [24 Power]
Number of Emitters: (up to 5 shots per round)
Targeting Systems: Class Beta (Accuracy 4/5/7/10)
Range: 10/30,000/100,000/300,000
Location:
Firing arc: 360 degrees
Firing Modes: Standard, pulse
Torpedo Launcher <18 x 2 = 36>
Standard Load: Type II Photon Torpedo (200 damage) or equivalent to Federation Quantum Torpedoes Mark I (400 damage)
Spread: 10
Range: 15/300,000/1,000,000/3,500,000
Targeting Systems: Class Beta (Accuracy 4/5/7/10)
Power: [20 + 5 per torpedo fired]
Location: one forward, one aft
Firing Arc: Self-guided
Torpedoes carried: 100 <10>