Hi Bob,
If you're looking at active speakers plus a preamp for $400, I'm not sure you can hit your target. The reason why I say that is because the speakers typically sold here on audiogon that are active are generally pretty pricy and are few and far between. If your absolute budget is $400 and you want active speakers, then you may want to see DJ-style active speakers on ebay.
The only other option that I can think of is computer/desktop monitor speakers that would be active speakers. At that point, you have KEF, JBL, and Paradigm as your choices that immediately come to mind. You'd have to find them used, as the speakers along top your budget.
In terms of preamps, look to NAD. They make great 2-channel preamps that are stellar. I had one that I sold only when I upgraded to multichannel preamps.
Good luck with your search.