Small speakers...big sound??

Totem Acoustic Mani-2 Signature. 8.5"x16.4"x12" and genuine bass extension (thanks to an isobaric woofer implementation) into the mid-20's and overall very linear with good in-room dispersion. Updated Stereophile measurements here.

1-20-09: Tpreaves
Check out the Zu Druid Credenza,they were designed for your situation.I have not heard them so I can't comment on the sound.

Then you don't just need small speakers, you need speakers voiced to sit on a credenza, like these of the (way expensive) Wilson Duette. I suspect that if you put speakers designed to be stand-mounted on a credenza, you'll be disappointed. Also at least consider getting some Auralex Monitor Pads.

If you can wait until they hit the stores, the new GoldenEar Aon series, especially the $998/pair Aon 3, looks promising. It's not listed as a product yet on GoldenEar's website , but it's been showing up at shows. Here's a picture and description . I've heard the GoldenEar Triton 2, which shares the same folded ribbon tweeter (a much evolved Heil AMT-style driver) and the treble is extended and smooth and the drivers are exceptionally well integrated. GoldenEar claims usable bass down to 38 Hz on the Aon 3's.

Oops! I just remembered another approach which might work for you. What if you got some compact omnidirectional satellites and a couple of "stealth" subwoofers? I'm speaking specifically of the Mirage OMD-5 satellites. The OMD-5's were originally $750/pair but are available from Vanns.com for $340-400/pair. With an omnidirectional radiating pattern, they are very room-filling. I have the OMD-15 floorstanders which use the same mid and tweet, and they definitely fill up the listening space.

The OMD-5s work best with one or two subs as the satellites are only rated down to about 60 Hz. The MM8 sub is a 1200 w (peak) 9" cube made to sell at $799. I managed to score mine at $279 from Vann's at eBay but it looks like that sale is off. They're a great match, however, as they are extremely fast and blend easily with a 0-360 deg. continuous phase control. Or you might get a pair of OMD-5's and get a single sub from somewhere else, such as SVS.

At any rate, the omnidirectional dispersion pattern of the OMD-5s gives them a big advantage in being able to fill a room, or even a larger listening space such as an open architecture cathedral ceiling living space. The subs would fill out the bottom. Bear in mind that in spite of their $340/pair closeout price the OMD-5s were designed to compete at $750/pair and have that level of dynamics, transparency, and linearity.