I used to have an NAD 304 and used PSB Alphas with it to very good effect. Since NAD and PSB are owned by the same "mother" company, they actually bundle Alphas with the NAD L40 as their "Music System."
I would look at the new Alpha B (around $200 online), or, for less money and a bit less bass, the discontinued Alpha Mini. You can get the Alpha Minis in cherry finish from Yawa for $132/pair (in white for $99!). The Minis originally sold for around $250-$300. I don't think ANY other speaker can touch them for this price.http://www.yawaonline.com/psbminbstoc5.html
The Paradigm Atoms, Axioms, and a couple NHT models are also great in the $300 range.