@twangy57 - As I mentioned before, the main indicator to identify a high current amp is does the rated wattage double as you drop from 8 ohm to 4 ohm. There are plenty of "modern" amps that are available. But, as you noted, the impedance requirement is definitely limiting your options.
Keep working on adjusting the speaker placement. It can take a lot of time and experimentation to get it right. Also keep in mind that room acoustical treatments (which can be as simple as a pillow in the corners or a couple of book shelves) will affect the sound. If you are having to turn down the bass, that is usually a indication that either placement needs work or you have some room issues.
I think you should try the CJ amp. It's not really an antique, just make sure it is functioning properly. If needed you can send it to CJ in the Wash DC area and they will check it out and fix it if necessary. They are a great company to work with. It will be a significant upgrade to the Adcom.
One last thing, I would strongly recommend getting a stand alone phono preamp to use instead of the one built into the Mac. You don't have to spend huge money there. There are plenty of choices in the $400 to $600 dollar range that should be a noticable improvement. (Even the Schiit Mani at $149 might be a step up and worth a try.)
In the end, going forward, take your time, do your research, and be methodical in evaluating and testing. And enjoy the music!
(Oh, by the way... current is spelled with an e, not an a. ...Mom was an English teacher... lol )
Good luck.
-Jeff