My wife and I are beginning to suffer the same fate, with difficulty making out the dialog on TV programs and Blu-ray movies. So, I have been battling this problem for years.
Actually, I find dialog is much more intelligible through the TV speakers than through outboard speakers. I think this is because TV speakers are voiced specifically to that end. But, if you are going to use a receiver and speakers, the speakers need to have really good tweeters and no mid range muddiness or resonances in the vocal range.
I put in a system for my parents with an Onkyo 608 receiver and a set of front L/R Legacy speakers(actually, I put in those Legacy speakers maybe 12 years ago but just put in the Onkyo 2 years ago). It is now a HDMI setup. It just sounds great, and dialog is very clear. Now, it may have something to do with the acoustic characteristics of their "den", as the call it.
For your parents, I would get a Onkyo 609 and a set of Monitor Audio bookshelf speakers or small towers. No need to buy new to get good sound clarity, as long as the drivers are in good shape. Monitor Audio are known for clear sound reproduction. I put a set of Monitor Audio Silver 9i in my two-channel bedroom system, and with that gold tweeter dialog is pretty clear, the best I have achieved in that room.
I'd also recommend, if you get some small towers, that you try to move the towers out into the room and as close as they will let you to their listening position, to optimize the balance between direct and reflected sound.
Actually, I find dialog is much more intelligible through the TV speakers than through outboard speakers. I think this is because TV speakers are voiced specifically to that end. But, if you are going to use a receiver and speakers, the speakers need to have really good tweeters and no mid range muddiness or resonances in the vocal range.
I put in a system for my parents with an Onkyo 608 receiver and a set of front L/R Legacy speakers(actually, I put in those Legacy speakers maybe 12 years ago but just put in the Onkyo 2 years ago). It is now a HDMI setup. It just sounds great, and dialog is very clear. Now, it may have something to do with the acoustic characteristics of their "den", as the call it.
For your parents, I would get a Onkyo 609 and a set of Monitor Audio bookshelf speakers or small towers. No need to buy new to get good sound clarity, as long as the drivers are in good shape. Monitor Audio are known for clear sound reproduction. I put a set of Monitor Audio Silver 9i in my two-channel bedroom system, and with that gold tweeter dialog is pretty clear, the best I have achieved in that room.
I'd also recommend, if you get some small towers, that you try to move the towers out into the room and as close as they will let you to their listening position, to optimize the balance between direct and reflected sound.