B/W 702 s3

B&Ws need high current amplification. You don’t need to bi-amp them with rotels. You need a high quality amp, good cables and some acoustic treatment. Look into Coda amplifiers. They’re high current design. Coda No.8 should be good. 
I would also recommend limited range bass traps in the corners behind the speakers. GIK Acoustics makes good limited range tri traps. This would help improve bass definition. These are good speakers that simply need a good amp. 

Looking at the specs for the Rotel, it doubles wattage into 4 ohms which is one of the hallmarks of a high current amp--I've often seen B&W paired with Rotel without any issue and often very musical.  I still think it's the room/placement

I auditioned the B&Ws with my Rotel amp and preamp.  Plenty of power at 350 WPC @ 4 ohms.  I found the B&Ws to sound too bright and sibilant over longer listening sessions.  I changed to different tower speakers and it sounds much better in my listening room.  Speakers have much more impact than the amp or preamp as long as there is adequate power in my experience.  I would change your speakers instead of chasing the right amp. 

@speedysteve4 

It looks like mixed movie music use with an AVR. If the only change was the speaker, then maybe you did not re-run room correction for the new speaker.

Also what Carver/JBL speaker are you referencing?

I have a pair 702s3's that are being driven by a PrimaLuna EVO 300 Integrated. And they are in no way lacking in bass. The bass is large, deep and defined. In fact, it is one of the most impressive things about the speakers. Maybe it is because they are being tube driven. The definition and detail that the speakers deliver across the entire frequency spectrum is amazing. I will concede to the fact that they can be a bit on the bright side at times, depending on the recording. But B&Ws are known for that. However, they do not lack the ability to produce low end. In fact I have had people ask me where the subwoofer was hiding. Because the bass was so deep and rich. If you are looking for a boomy bass that splatters across the other frequencies. These are not for you. In my situation, to add a sub would do nothing but mess up a well tuned speaker. I think that your amplifier is the culprit. If I can get the kind of bass that I am getting out of a 48 watt/ch tube amp. There has to be a better match for those speakers. They are well designed speakers and in no way should they sound mediocre. I will admit that my system really begins to shine at a higher volume level. Around 70 dB. Although below that level it sounds great. But it really starts to show its stuff as you turn it up. But that may have as much to do with the tubes as the speakers.