Pioneer A-351R Upgrade

Hello all,

I am a young 17 year old audio geek - not audiophile sounds to old :ROFLMAO: - looking to upgrade my Pioneer A-351R.

My dad bought it in 1993 for my Grandparents and it has brought about lots of joy over the years. From playing Madness, ABBA, Spice Girls, Ronan Keating, Bob Marley and lots of Salsa CDs, driving everyone mad with the same songs played all the time.

Until 6 years ago, when my uncle bought a cheap Toshiba TV and it had a 3.5mm jack to Audio and Video RCA connectors, where I had a idea of plugging it into a PC and piping Spotify through to the amp. To my shock it worked, and it truly did amaze me!

However, in the last 5 years I became more of an avid listener to the setup. So I upgraded the original speakers paired the amp from Mission 760i to Mission 751.
This made me appreciate the sound more as it had more low end grunt, and also a snuck in a Mordaunt Short MS309i which I bought from eBay to get some deeper low end bass.

But now I find to my ears the sound can be harsh sometimes and a bit muffled too, is there any components in this amplifier worth upgrading to squeeze some more performance out of it?

as I don't want to lose it just yet...
You can download the service manual (including the schematics) from hifiengine or elektrotanya.
Looking at the schematics - the only components worth replacing (in my opinion) would be the electrolytic capacitors in the signal path.
Whether you will hear the difference or not depends much on the initial state of your amplifier.
Another aspect there seems to be one version of it (HEWZ) which has lots of capacitors in the signal path (grounding it) that are not present in HE or HB models. Removing those - should they be there - could bring some life into the music.
But if you have no personal experience in this kind of electronics work then the risk of breaking the device during the mods is not small...