Hi Nathan,
103s, of any description work best on classic Japanese 'S-shaped' arms with detachable headshells, so Denon's own, from 'back in the day,' are ideal (many available now on ebay), but only entertain ones where the seller has tested the bearings, and has mentioned such. Another great arm for a DL-103 is a Linn LVV. Real synergy happens there (especially when used with an Audio Technica MG-10 headshell), and it's cheap...!
Here's a minter being sold with a Michell Focus One:
Also, arms from Micro-Seiki, Pioneer, etc, are ideal, especially if you can fit a 10" arm on your turntable. Most of these Jap arms were available in 10" versions, as indeed is the popular Jelco. 10-inchers, IMO, are the ideal compromise between 9 and 12-inch arms, and with a heavy headshell fitted, provide the ideal amount of mass that allows a 103 to really sing!
As an alternative, if you'd prefer new, a modern arm that works really well with a DL-103 (if you fit a high-mass headshell to it) is an SME M2-9R:
http://www.sme-audio.com/tonearms/sm...-m2-9r-tonearm
Essentially a 3009 revisited, but it's a bloody good arm, and musically far superior to a Series 300 (the one that SME and their dealers would prefer you to buy). Hope this helps
Marco.