A cell phone is a great medium for storing a personal music collection. Many people have transferred music from their CD collection into MP3s. That is a logical step because juggling CDs always has been somewhat awkward. Also, CDs will become scratchy over times and start skipping. The MP3 is the most commonly known audio format for storing music. However, there are also some other formats out there that are as good or even better than MP3. So when converting music from a CD, I recommend either using MP3 with the bit rate of higher than 384 kb per second or instead using a more modern compression scheme such as advanced audio codec. If you use AAC then you can get away with a data rate of 128 kb per second. The higher the bit rate the better the sound quality but the more storage space is required per song.
You can also stream music from online radio stations. Most radio stations offer different bit rates depending on your requirement. If you don’t have a fast Internet connection you have to dial down to a lower bit rate. Also, some online radio stations allow downloading of music to be played back on a cell phone later on. This is referred to as off-line listening. Note however that you need some storage space on your phone in order to do that. Also, transferring music onto your phone can be somewhat tedious. However, I do not recommend listening online from your cell phone unless you have a flat rate data plan. Using cell phones for streaming audio when using a data plan is usually more expensive than when streaming from a computer.
Unfortunately, the sound quality of cell phones is less than optimal. You really need some decent speakers in order to enjoy the music. I don’t necessarily recommend Bluetooth speakers because these types of speakers usually are a compromise between portability and sound quality. If you really are into high-end music then you really need some decent speakers. To drive the speakers, you can use a power amplifier. This amplifier usually has RCA inputs which connects to a cell phone headphone output. With your power amplifier can easily adjust the volume. If you do not like plugging in a cable into your cell phone every time you want to listen over speakers, you can also purchase a Bluetooth amplifier. A Bluetooth amplifiers able to stream data from a cell phone by using a Bluetooth connection such as audio. Using a Bluetooth amplifier with some good speakers usually gives you much better sound quality than using off-the-shelf Bluetooth speakers.