Investment is different than a purchase. Maybe you need to know more about amps so your purchase process is less risky?I'm starting to think buying used amps is too much hassle and not a good investment. Every one I've bought has need some work - usually to deal with rattles and hums. Sure, I save a few hundred bucks on the purchase, but then I have to go spend $100-200 on service, and possibly replace tubes within a few months. I bought a Fender 68 Custom Deluxe Reverb that is in great cosmetic shape for $720. Well, I get it home and discover it has a ridiculous amount of rattle at certain frequencies. Very discouraging.