Advice: used speakers $600


Choices: PSB stratus silver,Kef 104/2, B&w Dm7 mk2...any clear cut winner? I prefer a smooth, balanced sound, open midrange, controlled bass over extension.Also, which one of these requires the least maintenance in terms of upkeep.
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There's a pair of Silverline Preludes for sale here a little over your price range that have the sound characteristics you are seeking and are better looking than the Kefs and definitely the B&Ws -- Ick. Best of luck.
Monitor Audio RS-6 is a great speaker and grossly underrated, except for Bob Reina of Stereophile who used them to compare other speakers. It is solidly built, and has the cleanest bass of any speaker under $3000 I have ever heard.

You don't see them on Audiogon that often but depending on condition you should be able to pick up a pair for $650-700.They originally retailed for $1100

As Mr Soix noted the Silverline Prelude II (not the I) is also a very good speaker, but not quite the equal of the MA RS-6. in my opinion Good Luck
Second the Minuet Supreme Pluses for a small room, Preludes for midsize room. You will get midrange, pace, and tone in spades for little money.
Heres a really good one
http://app.audiogon.com/listings/monitors-audio-concepts-aci-sapphire-25th-anniversary-edition-2015-02-14-speakers-11209-brooklyn-ny