I’ve never heard the AT so unfortunately I can’t give a good comparison. I know there are reviewers out there who swear by the Denon 103 and review carts costing 4K+.

I looked up your amp. It appears to have a MM and MC setting only. There doesn’t appear to be any resistance loading options. When it comes to MM vs MC Lo, the physical install complexity is the same, but electronically they are very different. A MM cart puts out about 4mv, and required about 45db gain to get it up to line level. A MC Lo puts out about .3 mv and requires a SUT or about 65db gain to get it to the same level.

assume (assume being the key word) that your amp’s MC input is preset to about 60db gain and maybe 100 or 400 ohms resistance. There is a formula used for determining the appropriate resistance for an MC cart. The 103R has .25mv output and 14ohms impedance. The 103 has .3mv output and 40 ohms impedance. The formula is to determine the step up ratio required (5mv / cart output mv), square that value, and divide it into 47,000 ohms. This gives you the natural impedance of the input. The cart wants to see 10 times it’s internal impedenece. For the 103R, this means a 1:20 step up ratio and about 117ohms natural loading - and the cart wants to see something above 140. That’s about right. For the 103, this is a 1:15 step up and about 177 ohms natural input loading - but the cart wants to see more than 400 - that’s not normal. Normally, if your above the resistance, you’re OK. If your below, the cart gets ‘pinched’.

What does all this mean? The 103 is an OG cart and best uses if you have control over the resistance. The 103R has more normal specs and is probably more forgiving. Reviewers tend to say the 103R provides more ‘high end sparkle’ - if that’s what your looking for.

Needless to say - this is complicated. It’s more complicated than what o have here because the 103 is an unusual cart with a lot of history and folks who tweak the load to suite their tastes. Ideally you could find out what the load is on the MC input of the amp and let that be your guide. Better yet, someone else has heard both and can make a recommendation.