Audio Research REF 210SE Factory Upgraded to KT 120 (pair)

The upgrade makes them equivalent to the ARC 250. 

"Amazingly sounding, powerful and sophisticated" this describe the best this pair of mono locks. They can drive the most demanding and power hungry speakers (YG Hailey in my case)! It delivers excellent quality with crystal clear signal,  majestic stage and uncolored sound. Hard to find anything close to this quality at that price point. 
I am selling because upgrading a few levels up.

A new set of KT 120 tubes is available for purchase.

• 250 watts per channel continuous from 20Hz to 20kHz. 1kHz total harmonic distortion typically 0.5% at 210 watts, below .02% at 1 watt. Approximate actual power available at “clipping” 270 watts (1kHz). (Note that actual power output is dependent upon both line voltage and “condition” i.e.: if power line has high distortion, maximum power will be affected adversely, although from a listening standpoint this is not very critical.)

POWER BANDWIDTH
(-3dB points) 10Hz to 150kHz
FREQUENCY RESPONSE
(-3dB points at 1 watt) 0.5Hz to 240 kHz.
INPUT SENSITIVITY
1.7V RMS Balanced for rated output. (27 dB gain into 8 ohms.)
INPUT IMPEDANCE
200K ohms Balanced
OUTPUT TAPS
4, 8 and 16 ohms
OUTPUT REGULATION
Approximately 0.6dB ohm load to open circuit
OVERALL NEGATIVE FEEDBACK
12dB
DAMPING FACTOR
Approximately 14
DISTORTION
-
SLEW RATE
40V/µs
RISE TIME
1.2 µs
HUM & NOISE
Less than 0.3mV RMS - 106dB below rated output (IHF-A weighted, input shorted, 16 ohm output)
POWER SUPPLY ENERGY STORAGE
Approximately 787 joules
POWER REQUIREMENTS
105-130VAC 60Hz (260-250VAC 50Hz) 680 watts at rated output, 950 watts maximum, 380 watts at "idle", .15 watts off.
TUBES 
​8xKT​120 per channel (plenty of spare tubes included).
 1x - 6N1P gain and 1x1 6550C regulator.
DIMENSIONS
19" (48.3 cm) W x 8 ¾" (22.2 cm) H x 19½" (49.5 cm) D. Handles extend 1½" (3.8 cm) forward.
WEIGHT
74 lbs. (33.6 kg) Net; 89 lbs. (40.4 kg) Shipping. They will be shipped on a small pallet
Orginal boxes