Is it worth replacing an old amp?


Let me first apologize if this question has been asked before, I sure it has. I have an old 5.1 setup, Linn AV 5140 and 5120 speakers along with an old Yamaha DSP-A1 amp. The newest equipment I have is an OPPO 205. All my music is digital, where the vast majority being Hi-Res flac and dsf. The question I have is, would I get a noticeable increase in audio quality if I was to replace the old DSP-A1 with lets say a used Mcintosh MC205 or comparable?
divby0
Amplifiers sound different. Replacing your old DSP-A1 with a new amp o an old amp could change the sound and improve or worsen the audio quality. That being said, there have been significant advances in amplifier technology over the past few decades. Whether or not those advances sound better to you or not is something only you can decide.
You Probably would get better results. However it's still a HT unit which is made for movie soundtrack's. Music is second  thought. Imo you will get better results by going with a 2 channel amp. 
What you’re saying I agree with...I think. So if I read into this alittle, is it true then that if one particular amp sounds great with speaker X, that same amp might sound awful with speaker Y? I just assumed that if an amp sounded good on a given speaker, it very likly would sound good on just about any speaker (within reason). So I guess this is not true. Therefore, options would be, find a trusted person who has already made a comparison between a given speaker and amp, or find retailer that is willing to allow me to take home and sample the amp. That would make comparisons with high end equipment difficult seeing I’m looking to save $ and get used equipment.
Thanks...nothing is easy...
One possibility: check out online gear retailers that allow a home trial.

Some sell demo units. For example, here is a link to Crutchfield's current list of Integrated Amp Clearance deals:
https://www.crutchfield.com/outlet_category_4/Home-Audio-Outlet-Products.html?fa=1#&price=0-1200
They let you keep it for 60 days. 

Others sell used. TMR (The Music Room) offers a 14 day return policy. I've found them very pleasant to buy from and sell to. Here's their current list of integrateds: 

https://tmraudio.com/components/integrated-amplifiers/

Just my 2 cents...
My experience has been primarily with Pass and a few other brands over fifty years. An amplifier made by the same manufacturer will show significant improvements in ten years and a huge difference in twenty. It is a competitive market and to stay relevant a company must keep improving the sound. So, in general they all have. 

Companies typically have house sound, so, unless they took a turn (which could happen with a company like Yamaha) then you will get a similar but much improved sound with a much newer model.


I cannot comment specifically on recent Yamaha, the last one I owned was about 1980… it was supposed to be a high power amp (it weighed 75 pounds)… but the Acoustat 2 + 2’s electrostatic I owned drained it at low volume. The new Pass amp that I bought (Threshold s500), blew it away on power and overall tonal balance.