You can't run FM more then a few feet or FCC can shut you down and fine you or worse.
"Mr Microphone" and related products are legal but only has enough power to reach radios/receivers a few feet away. More can get you in big trouble and fast w/o correct licensing.
All it takes is 1 person at a show or a neighbor to the show to call FCC.
FCC may not come right away but they and cops can knock at your door or search your place looking for "Pirate Radio" equipment. If/When you cause interference to other license channels the more likely the FCC and cops will call on you.
BT WiFi and other signal strengths are regulated by FCC too even tho doesn't require a License to run. You can legally get better antennas that may help but boosting radio output is illegal in most countries. To the point if you follow WiFi news, In a nutshell FCC is/was trying to force WiFi makers to use locked radios and software because many users have moded firmware or DDwrt et al run the WiFi radio output above legal limits. WiFi in cities have big enough problems w/o some fool running their WiFi at max output the radio can generate ignoring legal limits.
BT has 4 classes w/ Class 1 and max ~100m but most BT consumer devices are Class 2 max ~10m or higher w/ less ranges. see
https://en.wikipedia.org/wiki/Bluetooth#Uses You can try BT but Most can't reach those distances because of crap antennas. Worse Most BT devices can't use better antennas w/o major mods. You can get BT speakers or plugin BT for any power speakers on Ebay, Amazon, etc. Plugins have USB for power and 1/8" "headphone" jack for audio out.
You also can try running WiFi 2.4ghz (WiFi G, N and AC) to get more range outdoors and connect remote power speakers to old laptop etc but may not reach if area is big.
5ghz WiFi has a shorter range and doesn't bend around or go thru building etc. 2.4ghz is better but doesn't like going thru walls etc either.
