Mr F: Regarding caps in the power supply(like that 1000uF): The more capacitance, the greater the dynamic range/headroom of the amp. If I were going to mod the power supply: I'd find Sanyo OS-CONs(http://www.diyparadise.com/oscon.html) of the same value as what was used. Whether the later X-formers were built off-shore, I can't Say(you might contact Dennis and ask him). I do know they are manufactured with grain-oriented Hypersil Alloy(http://www.mag-inc.com/pdf/twc-s2.pdf), and lots of it to avoid saturation. There are a number of other reasons(OFC close-wound conductors/air gap/acrylic insulation)for their quality, but the proof is in the listening. The preferences/opinions of the previous owner of your amps may have been influenced by a numer of factors, IE: Did he check the caps in both designs? Cary used oil-filled caps in a few different models/production runs, and they sometimes tend toward a euphonic presentation. Were both designs stuffed with the same tubes? Was all ancillary equipment exactly the same? If you liked the Sylvania 6SL7WGT, you'll love the TungSol 40's, round plate, bottom gettered, VT-229. Especially in the sound stage depth, mid-range liquidity and low level detail departments.