Decent preamp

Just another way to look at all this. When I listen to the identical preamp you already have into a  McIntosh amp with the exact same output as your Aragon 2004 I experience a pretty extraordinary performance on all fronts with exceptional accuracy, clarity and separation. You may possibly be trying to improve the wrong end of your system. Just a thought.

here’s a classic Eico, a bit over budget, $750. returns accepted. Has 2 phono inputs, and mode switch like McIntosh preamps do, many other features modern preamps have dropped, i.e. more inputs, balance, tones, loudness compensation for low volume listening ...

https://www.ebay.com/itm/Eico-ST-84-12AX7-6X4-Tube-Preamp-Stereo-Pre-Amplifier/233560836018?hash=item36614f87b2%3Ag%3AXcEAAOSwMmhel7om&LH_BIN=1&LH_RPA=1

have a look at it's innards, looks very easy to replace anything that goes in the future, very easy to spray clean all the controls ...

where are you?  I'm in Plainfield, NJ, 07062

If close to me, I have 3 fisher 500c tube receivers, all working, I could verify one in my system and let you try it, keep or return it. no shipping helps a lot on these old dogs.

stay 10 feet away, (we're retired, haven't been out for weeks) 

I'm in Chicago. That Eico looks good but I've never heard of the brand. Have you had a chance to listen to it?

No, I just did a curiosity search on eBay. I've never seen or heard one.

Eico was back in the day of buying Kits to assemble yourself, or buying factory complete assembled units. 

a budget brand, (with features and specs equal to the high priced stuff). It's a lot of preamp for that price, other brands, equal features, will ask far more.

https://www.hifiengine.com/manual_library/eico/st-84.shtml

https://www.audioasylum.com/forums/amp/messages/5646.html

http://www.tronola.com/html/st84_mods.html

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OTHERS....... Eico?????