Would the Denon 103 be a good match for ET2 arm?

Yes, the DL103 is a good match for the ET2. In fact, just about any cart will work well with this arm if set up correctly. The arm is only high mass in its lateral movement...its actually a medium mass arm that work great with higher compliance carts (ie. van den hul). The Denon will sound great though!

for the ET2 I would go for cartridges with a stiff dampening. The Denon is fine or the Zyx Universe, Atmos etc. I would not go for very sensitive carts like Olympos (especially the Lyras in general). You will ruin your dampening.