Do you know of small speakers that sound ''BIG'' ?

Totems - probably all of them, but I have personal experience with Mani-2s and Sttafs, and also, GMA Europa are worth mentioning. The Sttafs don't qualify based on your criteria as they are floor standers; however I would point out that Sttafs and other "small footprint" floor standers (of which there are many) take up no more room, and often less room than stand-mounts. For example, GMA Europas and Mani-2s should be mounted on 24" hi stands, which have a footprint of 12" x 13" or more, and a total height of 43". This compares to 7.5"x10"x35" for the Sttafs.

LS3/5a's sound much bigger than they are (which is tinny).
VSA VR-1 sounds big in a small to medium size room.
NHT SB3 gives great low end for a reasonable size bookshelf.
I think that most small speakers that sound big have a pronounced mid-bass bump that makes them more difficult to integrate with a sub. But if you are talking about a simple near-field set up it can be very pleasing.

Harmonic Precision Caravelles distributed by Star Sound Technology. Zu Audio Tones.

Silverline SR-17's. You won't believe you're listening to a monitor.

No, never heard anything small that even remotely sounded big....unless it came with a sub woofer