Vandersteen 2CIs or 2CEs can be easily had in that price range.
I'm personally on a Proac bender right now, and I recommend you check some out, esp. with your tubes. Their models with extended bass response are more $$$ but they do move used now and then.
I auditioned some of the new Proac Studio 140s the other day. Nice! They have the tweeter from the Response series, two 6.5" woofers and are floor-ported, which made setup very flexible.
Another good speaker that can be had used in the low-$1K range is the PSB Stratus Gold, esp. if bass is Job 1.
And Von Schweikerts, of course -- they are popular here for a reason