i had DB9 for a yr.
i wouldnt call it warmer than 303. its VCO is a Curtis 3340, and sounded very much liek it. - hard, focused ripping. 303 (which i had side by side) is comparably gooey, silky or edgy w resonance depending on settings.. i prefered its discrete VCO. tho both would have use in electronic setup.
filter on DB9 is interesting as its some kinda trasnistor ladder IIRC with 24dB/Oct slope. it can be modded to do 18dB/Oct slope, but i never tried this. all in all , great bass machine. surely punchier than 303. fast midi-cv control, nice setup of accent and glide control via midi. i liked it but in the end didnt use it as much.
if id have to pick one machine that sounds most like it right off the bat, it would be SH-101. which im planning to get anyway..
modular: roland system 100, mn/synthtech euro, nord modular g1
mono: minimoog, source, sem, sem, sh2, sh101
poly: obx, obxa, xpander, p5, a6, jp8, jp4, ppg 2, mw, xt, q, vs rack, d550, jd990
other: akai s950, solina, rhodes, svc350, förster