MU128 is better than MU100R: 1.MU128 is 64 part 128 polyphony, but MU100R is 32 part 64 polyphony. 2.MU128 add some new solo strings.

If you're not a YAMAHA fan, try the new E-Mu Virtuoso 2000,
features:
All-new 64 MB Orchestral Soundset (on two Sound ROMs) with 512 ROM & 512 User Presets
128-voice polyphony
12 assignable real-time front panel controls
Advanced synthesis architecture
Over 120 orchestral MIDI riffs
6 analog outputs + S/PDIF digital output
24-bit dual stereo-effects processor
2 additional internal ROM expansion slot
32 MIDI channels
Plays back Flash ROMs authored on E4 Ultra Samplers
Includes violins, violas, celli, double basses, trumpets, French horns, trombones, bass trombones, tubas, Piccolos, flutes, oboes, English horn, clarinets, bass clarinets, bassoons, contra bassoons, harp, orchestral bells, tubular bells, bell trees, celeste, xylophone, marimba and percussion battery with over 20 instruments
http://www.emu.com/products/virtuoso2k/virtuoso2k.html