I too cannot comment on the VP-100 because I went with the 150 (which works great in a 12-20ft room for me) IMHO I would go with the 150 for two reasons.
1. You may not be in a 15 x 15 room forever and 2. You won't have to suffer the with the agonizing upgradeitis "What if?" disease.
Mac

Denon AVR-3805
Denon DVD-2200
SVS PB1-ISD
Axiom Audio M80ti
Axiom Audio VP150
Axiom Audio QS8

“I feel more like I do now than when I got here!”