Hi, who has, or has had, modded their SET amps to much better heights than stock - either through tube rolls and/or by getting a techie to change parts. There are many amps like Cary 805 and Viva Verona that come used at nice prices but have stock tubes. The Viva 845s seemed to be voiced to the shuguang, but all other amps have 211s and 845s and other driver tubes can that can be modded. Any such cases around here?