This 2 speakers are different beasts. C3 is 2.1 speaker whereas Edifier R2730DB is 2.0 speaker + studio type (flat sound)

C3 subwoofer (8 inch) hit lower bass harder and deeper compared to R2730DB.
The R2730DB woofer (6.5 inch) is similar to a subwoofer but in stereo mode. Pretty strange experience though.

For regular usage such as movies, gaming, music, pick C3 (save some cash too!) or higher end 2.1 speaker such as 530D.
If you lack table space, or you table is occupied with monitors in Eyefinity setup. Go with 2.1 speaker (satellite speaker are small)
For music editing, go with R2730DB.

From the Edifier R2730DB perspective, you can listen to the original sound of the music author creates from without the additional treble/bass that the speaker colors with.
If the music developer creates music from C3 that has extra bass in it, when played with other speaker, that extra bass will be not existent there.