Modern A/V receivers are incredibly well reviewed and often have amplifier technology built in that works extremely well. Like with everything, you want to read reviews before making a decision. Be aware that these receivers often over-inflate their amplifier numbers if they were to be used for surround sound, but with two channels driven, they often respond extremely well.
Better receivers are really no different than two channel setups. They use better processing internally to convert digital audio to analog. They have better analog connections. They have better separation between the amplifier section and the pre-amp section. They use better amplifiers.
It often astounds me that there aren't more 'cheaper' pre-amps on the market. I really think with the quality that you get from entry level Denon, Yamaha, Pioneer, Onkyo and others, it would be nice to have them without the amps built in at all, but just a set of pre-outs from them to go to my own amplifiers.
But, at the end of the day, in the 'speaker setup' portion of every single A/V receiver of any basic quality these days, is the option to set the speakers to Left/Right front, no center, no surrounds, no subwoofer. And you have you 2.0 stereo setup done.
Be aware that analog audio connections are disappearing across the board and HDMI has really taken hold, so while an A/V receiver usually has plenty of HDMI connectivity, it may lack analog connections or much else. So, that's on you to recognize what gear you are connecting and how much connectivity you need or want.
I think the little Marantz units are pretty cool with their compact size and inclusion of pre-outs for stereo setups if you want to add an external amp. A few analog audio inputs, HDMI inputs, and a couple of digital audio only inputs. It's not huge, it's not crazy, but it is a nice little product.
http://www.us.marantz.com/us/Products/Pages/ProductDetails.aspx?CatId=AVReceivers&SubCatId=0&ProductId=NR1509
On a real budget though, there's certainly no reason you couldn't start with something like this:
https://www.accessories4less.com/make-a-store/item/denavrs530bt/denon-avr-s530bt-5.2-ch-x-70-watts-bluetooth-a/v-receiver/1.html
But, that's way out of line with what you have for speakers.