Ignoring FS-21 vs. SP-FS51-LR,
Originally Posted by xmai77
I recently purchased a pair of Energy CF-30 floorstanding speakers for a really good price but I can't decide whether or not I want to keep them. I've demoed the new Energy towers and I find them much brighter than the Pioneers, but I haven't really had extensive testing yet.
Your question really reduces to one of which set of matching speakers you prefer for your entire listening environment once properly calibrated to the room, which leaves the operative question being
Lastly, what's a good way to audition speakers?!
Move between two isolated proximate identical rooms (except for the speakers) playing the same variety of material, spending long periods of time in each over a longer period. Next best is flipping back and forth in the same room like in a typical audio demo room, but not one speaker at a time.
Since you have just the Energy floorstanding speakers, a good practical test would be to spend time listening just two channel sound (even when you have surround sources) with each being properly calibrated for the room. This requires support from your receiver, else many re-calibrations (which will interfere with useful quick A/B testing). If you develop a strong preference for the Energy speakers, then you can buy the rest and replace the Pioneers. Otherwise you might want to use them for two channel work elsewhere, such as for an office*.
This might not be the right thread for good advice on Energy speakers, but I'm sure you won't have to go far to find one.
*[That's where I have my SP-FS51-LR and SP-BS41-LR.]