Should I consider the newer Audio Research pre & power amps, when I play records not CD's

ALL dealers are more into A/V systems.

I have some bad news about your aging hearing -- you can still tell the difference between a $10,000 unit and one that will set you back $50,000.  So don't think you are going to get off with a blissful old age listening to a boom box.

The the quality of the turntable matters, but some design criteria do not matter because you can avoid vibrations in the room and air since you are not pumping out any SPL when making the transfer to your digital library.

iFi and anything with 'dragon' in the name will be good analog to digital converters, but you can always spend more to truly capture the best rise times and decay on those snaps, pops, and crackles on your vinyl.

I had the VT 100 (original model MKI not the MKIII), it died last year.  I was a little worried that the Ref 75 would not have enough power to drive my speakers, Aerial 10T but they sound great!!  The Ref 75 has a much cleaner and accurate sound in my humble opinion but the technology is 20 years newer too. 

I just finished a long session tonight with my ARC D70 mk2. If you are interested in an amp that can now be had for not huge money, and want a giant killer, imo this is the amp for you!
i have ’AB’ ed this amp against the later VT series and the classic series, it was really no contest!! The little D70mk2 just kills them!
Now , as usual there is a price to pay... the age of this amp dictates a couple of things..you will need to have the amp set up by a tech, the biasing procedure is a nightmare, plus you will need to get cables with small spades only. This due to the old fashioned speaker connectors that the amp uses. However, if you accept these issues, I believe you can acquire an amp that imo has little to no competition....even today. WZJ hit one out of the park with this amp and the highly sought after monoblocks... the M100’s. I suspect these amps were his zenith! And what a zenith they are!

I have read and heard from you'll that the ARC LS 25 MKll is a good pre amp in the lower price range. I know the ARC  Ref 2mkll and the Ref 3 are better. They seem to never show up for sale. Why not consider the LS 26 and LS 27 over the LS 25? Just some opinions.

When hooking a DAC to my computer I can use USB and I also see an optical connection near my speaker jack. Which is better to use to get the siginal to the DAC?