For the earlier Virus models (Virus A and B) it used to be almost as simple to calculate as you mentioned Simon, however as Boreg stated the TI and TI2 are different as it appears to be more a global CPU issue. The more complex the oscillator, signal flow and effects, the fewer the poly, and vice versa. You should get stacks of poly with the TI2 in normal use though.
PS> Congrats on the TI2 Polar.
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PS > And another thing! Will the Ti|3 have user customisable/importable wavetables?
A ribbon-controller or XY-Pad might be nice, too, please! Thanks!