I normally as a habit DON'T chime in on these threads,but I MUST second Amandarae's suggestion regarding the Altec Peerless 4722.
I too own a DL-103 (not "R") and just so happened to have a vintage circa. 1978 Denon T-320 step-up that was mated with a damaged 103.At first I was VEY satisfied with the sound ,as I figured this was how Denon intended the it to sound.
Well! I really can't tell you why but I ended acquiring a custom made Altec 4722 step-up and all I can say is WOW! this really let the 103 "breathe" the sound be came more nuanced,detailed,more texturally DENSE,,,etc,etc. and EXPANSIVE ..... try it you'll see
I also believe the BOB Devices' SUT are very good as well they are very well designed although for a little more coin.
I would start here and then you may be satisfied with the changes rendered.Question does the McCormack have a MM input? If so you would need to have the 4722's wired for a 38 ohm load.I had mine built with a toggle that allows me to switch between 38 & 100ohm resistance.
If you have any questions feel free to private mail me