Re: help with solo
i agree with bammbamm that the context is everything here, but if both chords are played for the same duration, and assuming that the 2nd chord is the 'resolving chord', i wouldn't settle on one mode for the entire progression. let's break it down on a chord basis:
first chord is a C9 and the 2nd chord is a Emin6 (in 2nd inversion, since the B is the bass note). it's a cool sounding progression and should allow you to milk some great tension notes.
looking at the chords individually, the obvious choices for the C6 would be C major, C mixolydian (there is no 7th in the chord, so this is ok) or C lydian. you won't have as many options on the 2nd chord, as it has that natural 6th. your best option is probably going to be E dorian.
when i play over the progression, i naturally tend to gravitate to the C lydian - E dorian option. probably because with this option, you only have to change one note between each mode (c to c#). the other notes stay the same, although the tension notes and key chord tones are of course different. the other options (C maj & C mixolydian) would require you to change 2 notes. this is ok sounding, but the c lydian to e dorian options sounds less 'obtrusive' imo. good luck and happy experimenting.