The Vandy's are usually 6 to 7 ohms nominal impedance. Importantly, Vandersteen speakers tend to be an easy load to drive since their impedance does not vary excessively with frequency (IOW, the "nominal" impedance of a speaker doesn't tell you all you need to know about driving it.) Unless your room is unusually large, the Yammi should push them just fine. I got my 1Cs when I was using a Pioneer Elite AVR rated at 90 watts/channel. I had no problems with loudness. I will say, however, that as I have upgraded amplification (currently using an Odyssey Stratos HT3 rated at 150 watts/channel), the quality of the sound has improved. The 1Cs might be a little weak in the lower octaves, IMHO. Without a subwoofer, I would shoot for at least the 2Ce if you can.
Need speaker suggestions
I've just about finished my "game room". Ceiling and walls are drywall, floors are wall to wall carpet. I have a really old pair of Cizek speakers(circa 1975) in there for now and I'm using Zone 2(100w/ch I think) from my Yammy receiver to drive them. Other than the pool table there is no other furniture in there now and probably will only be bar stools(with the bar of course) as future furniture. Room is very bright, may add some acoustical treatment at some time....but with the given descriptions what speakers would go well with the "brightness" and the fact that it's Yammy's Zone 2 powering the speakers. I've heard Vandersteens and like them but will they mate well with the receiver's second zone output?