Herron VTPH-2A easily hits all the notes you require. I have one an it sounds awesome! Handily beats my Rogue Ares Magnum, which itself is quite a good phono stage at its (very similar) $3K price point. In fact I just swapped Ares back in last night to check/compare and holy cow...that didn't last long! The Herron offers flexible loading via RCA plugs, perfect gain structure for your Kiseki (I use mine with a 0.5 mV Shelter Accord and 0.45 mV Orotofon Cadenza Bronze), very quiet, liquid midrange, excellent resolution and dynamics. Sounds very clean, neutral, and linear with just a touch of the tube sweetness/magic. I stocked mine with four Telefunken smooth-plate 12AX7 and an Ei Yugo 12AT7.
Definitely weighs a good bit less than 38 lbs (I think low-20's), but not as light as the super-compact SS units - you'll be sacrificing way too much performance with those, anyways. The VTPH-2A is only beaten out by my VAC Renaissance SE phono stage with Koetsu Coralstone (the ultimate in a romantic yet highly resolving sound), at more than 3 times the price (not to mention the Coralstone's cost)! And the Koetsu might be a special case because those 0.3mV Platinum motors seem to really, really want to be paired with the right step-up transformer. Whereas cartridges in the 0.5mV range (Ortofon Cadenza, Shelter Accord and Harmony) seem to do extremely well with a FET stage like the Herron's.
Your Kiseki is an unusual case at 41 ohms and 0.5mV, but that will be no problem with the Herron's flexible resistor loading and 2 gain settings. Given how great that Kiseki is supposed to be, I'm guessing this might be a dream match. I recommend you call up Keith Herron and talk to him about your needs.
