Shindo Allegro 604s

[tiger1967]

Hello, I am new to this forum and I am new to Shindo. I recently acquired a preowned Shindo Allegro 604s preamp. It really changed the way my system was singing and I enjoy it very much. Unfortunately I have not been able to find any information about this particular preamp. It is not a complex piece of equipment and I do not really need any manual, but still it would be great if anyone could point me in the right direction to where I can find some info about Allegro, technical data, years of production, goods, bads, etc. The preamp is far from new but is in very good condition. I noticed that tubes are GE and Mazda 12AX7. I am planning to replace them with Telefunken tubes. Would you recommend such upgrade? How can I find out which tubes were there initially?

On another matter: my speakers are JBL K2-S5500, 4 ohms, 95 dB, recommended amplifier power 100-300 watts. I currently use vintage Sansui BA-5000 to power up the system and it will soon be replaced with vintage McIntosh MC2300. As you can see they are all solid state amps capable of producing big watts. Would you recommend any Shindo gear that will manage my speakers?

Regards,
Evgeny