Need some advise please on a 30 year old system

By all means keep it and use it, all of the equipment listed is high quality! I would invest in a variac transformer to use when first powering each piece. This will reduce the chance of electrical damage after not being powered for so long. The turntable will need some TLC and lubrication most likely. 

You said these were in storage for 8 years, was the system operated before then? If off for 8 years, that's not too long for an SS amp. The Spectral preamp has a separate power supply, so you can power up the power supply without connecting it to the preamp itself first. I have not had a problem with bringing SS equipment up to voltage relatively quickly. Say from about 50% of line voltage to 90% line voltage in about 2-5 minutes. Then go up to the full voltage slower, maybe 1 hour from 90% to 100%. After bringing the power supply of the Spectral to 100%, let it run for a couple hours or more. Then turn off and the next day, connect the preamp to the power supply and bring the voltage up to 90% in 1-2 minutes. Again go from 90% to 100% in an hour and let it run for a while. Follow similar procedure for each power amplifier separately, 2-5 minutes 50-90% then 90 to 100% in an hour.  I'm sure others in the community will have comments, so I encourage you to wait to get more input. If you want to message me, feel free.

Don't let anyone low ball you on price for this equipment. The last Infinity IRS Beta's on US Audio Mart in 2017, listed for $7400. Probably worth more now. This equipment is very good stuff. Good luck!