I’ve had my SLP-05 for 6 years now. I did an upgrade to the unit with Cary 18 months ago and I still swear by it. To gain any appreciable improvement you would have to spend an inordinate amount of money and then you may actually notice some difference. I think the larger question is that items falling off the ‘A’ list in Stereophile is a mixed bag at best. Why? They have their favorite items they like to maintain and the others they might grant an ‘A’ rating and then drop later on. For instance. I own the Aesthetix Rhea phono pre-amp, ‘A’ rated and then the following report period they dropped it. The ‘A’ rated Rhea has not been changed in 6 or seven years, unless you buy an upgrade. Want another? My Turntable is an Oracle MK-5, it has now been upgraded. But prior to the upgrade it was an ‘A’ and after 6 months it was dropped as well. I have a Myabi stereo cartridge from 47 labs for my T/T. This little unit has been an ‘A’ for years. But after 6 months they dropped it off. We all know there are any number of shinatagains behind doors. Even my main speakers, Coincident Pure Reference speakers were ‘A’ rated 6 or 7 years ago by both Stereophile and TAS. TAS gave a very nice write up and report about this speaker and Stereophile said an OK two page write up and then 6 months later dropped them off like a rock. If you notice Stereophile has their regular group of speakers they return to every couple of years. Look at the Linn turntable. This has been an ‘A’ listed item for literally years. There are so many upgrades and purchasing options the entire unit should have been dropped off 5 years or more ago. When was the last time you heard of major write up on it?
there are many new and even brand new highly efficient speakers and even many low efficient speakers as well. Hopefully everyone realizes that efficiency plays a big part in the speakers being chosen for your home. Yet that point is never brought up in any Stereophile discussion for the experienced mind or the inexperienced audiophile.
Finishing up, I still think your purchase of the SLP-05 is still current, other than the digital domain we have to find alternative work arounds to remain true to all formats. You have a well built and truly awesome unit. To replace it? Prepare to spend 16K and up to match. Then think about the PassLabs 17K pre-amp. Too much for retirement checks!