Good luck with this sale. I had a similar Net Audio modded 33/303. Transformed the sound of the original and I think you would have to spend a lot more to get a noticeable increase in SQ.
The guy I sold them to a couple of years back is still very enthusiastic about the combo. Your price is very fair.
Analogue: Linn LP12/Keel/Karmen/Karousel/Tranquility/Radikal/Trampolin 2/Collaro mat/Ekos SE/Audio Technica ART-1000 into Gold Note PH-10/PSU-10
Digital: Cyrus CD XT Signature into Border Patrol SE DAC
Amplification: Modwright LS36.5 pre into Modwright KW150SE
Speakers: Boenicke W8
Interconnects: Reference Fidelity Saturn and Oriton Orange Symphony
Speaker Cabling: Townshend Isolda
Headphones HD600
Mains: Various MCRU kits/Russ Andrews Power Cords/X Block
RCM: Velvet Vortex Ultrasonic