The Shelter 501 Mk 2 works without the fluid damper but you owe it to yourself to put the fluid damper on as it provides the biggest improvement in the arm. I ran the Shelter without but after hearing my old table with the fluid damper on I probably wouldn't have sold my Technics. I used the stock headshell and didn't need the extra weight on the back of the arm, but with a heavier headshell the extra weight would be required.
The Denon 103 requires another 3gram brass weight on top of the cart if I remember correctly and the rear weight. The Denon 103's require a really good MC phonostage or a step transformer to sound their best as they are ~.2 mv, whereas the Shelter is .4mv and that's a lot of difference, plus you could get interference from EMI/RFI if you haven't used a low output MC, so remember you might have to spend more on the phonostage to get the most out of the Denon. The Shelter has a much more neutral presentation and way tighter bass, plus the Shelter has a better elliptical stylus and won't wear your records with it's 1.85gram loading versus the 2.4-2.6grams I think the Denon needs and it has a conical stylus.
The Denon 103 requires another 3gram brass weight on top of the cart if I remember correctly and the rear weight. The Denon 103's require a really good MC phonostage or a step transformer to sound their best as they are ~.2 mv, whereas the Shelter is .4mv and that's a lot of difference, plus you could get interference from EMI/RFI if you haven't used a low output MC, so remember you might have to spend more on the phonostage to get the most out of the Denon. The Shelter has a much more neutral presentation and way tighter bass, plus the Shelter has a better elliptical stylus and won't wear your records with it's 1.85gram loading versus the 2.4-2.6grams I think the Denon needs and it has a conical stylus.