The operating range of the Bellari is 3 to 6 mV. The factory spec output of the DL-160 is 1.6 mV, though they test out to 2.2mV according to Needle Doctor, but that's still too low for the Bellari.
The 2M Blue is one of the best things you could possibly get for $200 for an RB250. They also have high output, even for an MM. The next step up would be the Audio Technica AT150MLX, available for $299 at
http://www.audiocubes2.com.
I have both a Denon DL-160 and an AT150MLX. After reading the first half of this thread, I decided to listen to them back-to-back as a sanity check. For me it confirmed that the AT150MLX seriously outclasses the DL-160. On its own, the DL-160 sounds good--even tonality, decent tracking and frequency extension, and good body to the sound. Plug in the AT150MLX, however, and you keep all those good things while it also shows you all the music you've been missing. It pulls out a wealth of instrumental timbre and ambient detail that the DL-160 misses on my rig.