Advice please.

Given the style of music and the volume levels you play it at. I would look at Zu Audio. Klipsch is another speaker to look at, the vocals are fairly loud in the treble region so you may enjoy the way Klipsch projects music. Zu audio would be my first pick though. 

Thanks.

Jump on used Josephs audio great sound and company!!

+1 on the Acoustic Zens! I used to own a pair and really, really enjoyed them. Moved on to my current Spatials only because they pair better with my amplifier. But the Adagios are killer speakers that resolve beautifully no matter the volume.

Try giving Robert Lee a call (he makes them). Tell him Simon recommended you talk with him. I doubt he'll remember me but I called him on the advice of another Audiogoner who recommended AZ's and it was a pleasure talking with Mr. Lee and perhaps getting a deal on his speakers.

You say you don't want to add a subwoofer but in the next breath you want to improve "especially the bass".

A subwoofer or better yet, a pair of subwoofers will give you the most flexability for the quest of better bass. The biggest advantage being able to move them around the room to the best location for the least amount of cancellation. They also have the advantage of adjusting the phase which has a huge effect on bass frequency cancellation.

Subwoofers give you far more flexibility to properly tune the bass frequency than having the restriction of floor standers in a set location.