Yamaha YST-SW800 parts

Hi,
I'm fixing faults on the sub power amplifier, and need to replace two output transistors 2SK2378.
They're avaible at Yamaha Technical Center but the price is amazing, at least 25 eur each + shipping ... and that for a 13A 200 volts FET !
I tried some FEt's like 15N60C3 or IRFZ40 but there's 0 mA idling current with them.
Could anyone tell me where to find the original components at a realistic price or advice an other Fet that would work ?
Thanks in advance ;)
 
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No idling Q16 / Q18, no voltage across R30 / R35.
If Q16 is a 2SK2378, there's an idling current across R30 with or without signal, and 0 mV on R35 if Q18 is replaced by IRF type
If Q18 is a 2SK2378, there's an idling current across R35 with or without signal, and 0 mV on R30 if Q16 is replaced by IRF type
 
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