Audio Research, next upgrade?

I found the upgrade from the ARC CD3 MKll to the ARC CD5 very worthwhile. Not familiar with your other gear.

Bigger amp. More power and the speakers will sound even better.

I would actually keep the CD3 and get a decent DAC (better than the DAC in the CD3). I bet the CD3 is great as a transport and if any upgrade is needed, it would be the DAC. Also, a REF 3 or REF 5 would be a definite upgrade. But, listen to a REF 3 and REF 5 in your home if possible with direct comparison with your LS26 first.

enjoy

First,
Update the fuse in the CD3 MkII (I suggest a Furutech-make sure you install it correctly). This is a low cost change the works.

Second, update the power cord inthe CD3 MkII to a Shunyata Black Mamba CX version.

Third, update the fuse in the VT100 MKII, then try updating the power cord, use a shunyata CX Black Mamba here too.

Fourth, if you have a little more money, I would update the amplifier to a ref 110 or ref 150 or the CD player to a DAC8 and use my computer to playback WAV files.

Get a vinyl setup if you have the space and the desire. It's going to make a bigger impact on sound than any digital or amplification element you could possibly buy.