Xiaomi Mi, Kenwood AS-BT77, RIVA S, JBL CHARGE II PLUS, Dockin D Fine, DOSS SoundBox XL
My rating of the best speakers:
micro
$35 Mi Bluetooth Speaker, model MDZ-26-DA plays flac from the memory card. Extreme ratio of bass / size.
The disadvantage is a little muted high frequencies, not very pronounced stereo effect.
mini
$150 Kenwood AS-BT77 - the best universal speaker. Separate amplifiers for stereo drivers and for a subwoofer, high accuracy of sound reproduction,
excellent stereo effect and surround sound in 3D mode. Small battery 1600mAh, but 7.4V. Playing from any external Powerbank.
midi
$90 DOSS SoundBox XL - plays flac from the memory card, sounds like Hi-Fi, reproduces the low bass.
It does not have dome tweeters, so the sound is slightly directional.

€140 Dockin D Fine - powerful sound, no distortion at maximum volume.
At high level of the input signal from bluetooth or by cable (average level of amplification) Dokin D Fine sounds like Hi-Fi.
Want more bass - reduce the level of the input signal and increase the volume on the speaker.

Wireless Portable Speaker's:
http://www.mi.com/en/speaker/
http://www.kenwood.com/jp/products/audio/personal/as_bt77/
https://rivaaudio.com/riva-s/
https://www.jbl.com/factory-refurbi…/JBL+CHARGE+II+PLUS.html
http://www.dossaudio.com/en/productMore_1367.html
https://www.dockin.de/d-fine/
Hi-Fi-players:
http://www.fiio.net/en/products/39
http://hifiman.ru/products/hifi-players/hm-603/