The RWA amps use a pair of SLA UB1250 F1 12 Volt 5AH batteries. Easily available and can be had for $12.00 each. No worries about future availability. I'd be more concerned about sourcing a favorite vintage NOS tube in 20 years.
digital Amp. Going green
Any thing out there between $3000 to $5000 in the digital amp arena that has altered your desire for using tube base amplification?