Adcom 535L upgrades?


I have an old Adcom 535L amp (60wpc) from the 1990s. It's a utility amp and actually sounds decent if a bit grainy in the mids and highs. I'm not going to try to sell it, as it doesn't promise much on the used market. 

I'm wondering if anyone has replaced caps or other key parts in their older Adcom gear and if so whether (a) it made a real difference and (b) how much it cost? 

Thanks.
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Thanks, guys. I do like it. Will report back if I find a local tech.
Musical Concepts/Musical Design may be a rebuild or upgrade path as well. They are not cheap but their work is top shelf.