Has anyone tried one of these cool portable amplifiers? It would be PERFECT for jam sessions. I wonder which one of these is the best. https://www.amazon.com/PWMA50B-Waist-Band-Microphone-Rechargeable-Batteries/dp/B005I2YJPM/ref=pd_lpo_267_bs_img_2?_encoding=UTF8&psc=1&refRID=29DYXJPXH5GHNTA4XEV5#HLCXComparisonWidget_feature_div