for 5.1 generally you have two choices:
htib sets (home theater in a box)
complete home theater ( separate receiver, speakers, subwoofer... or sometimes sub+speakers are kit and avr is separate)
htib tend to be cheaper (tend, but not always) but you need to be careful that they accept 5.1 input via hdmi or optical. many cheaper models lack 5.1 input even if they support hdmi arc or optical so you need to check. many cheaper models only allow 5.1 from the integrated dvd player. another negative is that the speakers are sometimes 4ohm impedance which makes getting a replacement amp later on more difficult. the benefits are that they are generally cheaper, everything is included in one box and sometimes have smaller speakers.
complete...