Firstly welcome to HFV....noticed you joined a couple of days back last week!
There are a variety of brands and models available with the multiple dealers in the market...all depends on what suits your tastes in terms of budget, performance and expectations......
You need to audition the systems which are available and make a list of the ones that suit your needs and wallet......then share that list with us....we can help to steer to the possible best one from the list.
There are first hand comments and feedback from users of Yamaha or Pioneer or Denon...there are dedicated owner threads which you need to refer to which will help to understand better.
We all can recommend a lot, it is upto you to decide what sounds good and fits your budget......what will be your sources? Are you planning to connect your PC or Laptop? Does the PC or Laptop have a proper soundcard which can / will send out proper 5.1 signals to the AVR? If not then you need to reconsider your purchase accordingly...
All the best!