That is a good question, I wonder myself too

I wonder if I would really notice a difference...
The Ref 20 is getting long in the tooth. I think I got it around '98-99. One input is out, luckily you can rename the inputs

It's always been slow - the sound always starts about 5 seconds after the image or you miss the first few seconds of a CD. There's no HDMI input/outputs on it. I've also run into decoding issues with some Dolby Digital formats (I found a setting buried in the blu ray player that allows me to overcome this). It's also only a 20bit/48khz dac/adc.
My second remote, HTM MX-500, is dying and it doesn't support any of the newer standards so you can't program it to do much else.
I'm also seriously considering going to 7.1 by moving the Acurus and picking up a 2channel amp off ebay for the two channel system.
On the other hand, I've worked around most of these one way or another and have thought about running it until it dies. Yet, that seems pointless too...
The monitor 50s aren't that bad and serve their intended use. They fill the living room and kitchen with music which is almost always on (we're all musicians in my family). I thought you'd rip the Adcom if anything. It seems people like bashing these on all these forums. All serious listening and viewing is done in our "screening room."
Thanks.