Paradigm Studio 60 v5 somewhat boomy

I find the bass slightly boomy, and not well controlled at times. otherwise is quite good

is there anything I can do to cure the boominess a little?
Yep, boominess can be readily attributed to your walls and room. Try placing them further away from the walls both side and rear. Also, maybe if you have a finished basement, in my experience this is your best listening room due to the cement walls. I have the same 30k audio system and have used it in 3 different homes, each has had its issues with boominess, except for the finished basement with cement walls.
I too have the Onkyo A9555 running the Paradigm Studio 60v.5. Initially I had my speakers about 5 ft. from each other, and the bass seemed a bit boomy, and the soundstage was not that great. I adjusted the speaker position, allowing more room between and behind the speakers, and not the bass is awesome. Tight and fast. The imaging has improved dramatically. It's all about proper speaker positioning.

I see you have ordered the Signature S1. Unless you use them with a subwoofer, you will seriously miss the bass.
These speakers are not boomy by any means if carefully placed (at least 3ft from any wall or another speaker). If anything they are on the taut side, at least when compared to most other speakers I’ve had in my room. I had Studio 60v3 and they were much riper in the low end, perhaps a bit too much. The v5s are capable of tremendous transparency, neutrality, drive and impact if paired with the right equipment. They also throw a huge and seamless soundstage and have surprisingly deep bass for their size. I have not heard a better 2-way or 2 1/2 way system in my setup all things considered.
Young at heart,
which speakers are you getting?  Theres no version 6 of the signature 1...

im confused.

I’ve had numerous Paradigms and the Studio 60’s that you have are not boomy.  Perhaps bright but not boomy. Something else is going on.  Placement, room treatments, amp...
as far as the Sigs, go for the version 2 with the berrylium tweeter