Just bought my self a S330D.
What soundcard is on par with it which will not bottleneck the performance?

From outside, yes the driver difference only 5 inch woofer and 6 inch woofer. But inside, R2600 used bi-amping Class D amplifier, a rotary digital volume control and tone control. R2500 still using the previous model amplifier TDA2050 which is still sound great and combine with + and - digital volume control.

R2500 for about RM38x and R2600 for about RM46x if not mistaken, if you need more bass try get R2600. R2500 gives sufficient bass for normal listening but most would said not enough bass.

R2600 bass response is better, not sure about the bass loudness when compared to C3.
If you like loud low frequency bass that fills up the whole room, I don't think R2600 suits you but try audit it before you decide. 

R2500 and R2600 are good for all genres 
The bass I mean is loudness of low frequency bass, like about 80hz or below is not that loud makes you feel like something missing.

Both R2500 and R2600 only the loudness, bass volume and your budget are up to your decision, it won't produce one note bass don't worry.

Remember to have a good speaker position once you have it, I found it very important in Edifier speakers.