My Silver Mono's need output tubes, but they are at Audio Connection in NJ and John has 88's or 120's to install depending on what the person wants. Without cages, the last Silver Mono's went for north of 1500 at least. Yes, they are going for that as folks realize who well made they are and how great they still sound. Mike makes gear that lasts and can drive anything. Silver Mono's were some of his best amps he's ever made in regards to power and sound. I've heard folks do upgrades on them, but they didn't make them sound better. Good luck as they are worth it, but not many of us are selling. I also am selling my original full function Quick preamp that rocks and I think sounds better than his newer preamps as so many others. I'd love to sell these as a package as they sound perfect together.