I have just purchased a DS225 which has replaced an aging Gryphon S100 power amp. This latter was no slouch when it came to power and tight bass control especially but was starting to show its years. The rest of my system is front-ended by a Wadia 381i and Sonus Faber Liuto floorstanders. Cabling is by Cardas (speakers) and Crystal Cables (interconnects) and the Wadia is fed by an Isol-8 mains conditioner which is, in turn, supplied by a Pragma mains filter. The sound that results from this set-up is amazingly good. I have no experience of the DS 135 so cannot compare. Suffice to say that I cannot think of a more natural yet detailed sound than that which I enjoy today.