"The LA-150 is a seductive preamp... "
There are three LA-150: Mk1, Mk2 and SE - from your description it seem that you have Mk2. Indeed very lush and 2007 Golden Ear Award winner. Mk1 - is lean and I don;t like it.
" sweet and delicate treble, though not extended" - definetely Mk2 and not Marienne-Electra preamps (300 and 450), as latest ones have vastly extended "magical" HF - thanks to Simon's lenghly investigation of best V-Caps in variety of equipment, see -
http://v-cap.com/simon-thatcher.php
These capacitors, as implemented lately, also increase details, I been told.
" ... full (perhaps overly so) bass, though a little loose"
- may be (Harry Pearson liked LA-150Mk2 bass - see his review on J-E web site)...may be for some. Then go for LA-150 SE or even better for LA-300ME (or 450) with their special power supplies. Jud (and Simon) are fanatical about power supplies. No suprise, every serious designer is but to do it right, its different matter.
Finally, yes - Simon work very actively with both Spectron and Joule-Eletctra so both, at least partially were voiced together on Simon's system and thus there is great synergy. My LA-300 - Spectron monoblocks - B&W802 Diamond is the music heaven !!!!
