Belles 350A Reference vs. Pass INT-150

Hello, I am currently running an Opus 21 cd player pre-out
to Belles 350A Reference to Dynaudio Special 25s. I'm wondering if the Pass INT-150 has significantly: lower noise floor and finer midrange to high frequency detail, plus better imaging than the Belles, or would this be a lateral move? Would appreciate any comments from someone who has compared INT-150 or X---.5 series with the Belles.

Also needing more inputs, so considering adding a pre-amp to the Belles instead of switching to an integrated. I liked the natural detail in the (discontinued) Herron solid state pre-amp, may consider one of the more recent Herron tube pre amps.
I owned Belles 350A Reference monoblocks, and I compared them to a Pass Labs XA-30.5, and later to Pass Labs XA-60.5 monoblocks.

It wasn't a close contest. The Belles are very good. The Pass Labs amps XA-.5 series amps are exceptional.

I expect the same would hold true for the INT-150.

IMO, it would definitely be a move up.
The INT-150 is based on the X.5 series rather than the XA.5 series, so it presumably gives something up to the XA's in refinement in exchange for the extra power.

The INT-30A is more directly comparable, being basically an XA30.5 with a passive volume control and control circuits.
Good point Auxetophone.

I still believe the INT-150 would be a step up from the Belles 350A Reference, but as always the final determination is in the ears of the listener...
The latest stereophile has a review of the INT-150, and he does compare it against the XA-30.5 and I beleive the Rogue Monoblocks - so it may be worth taking a browse through that to get an idea of its personality (at least in the reviewers system and opinion).
If you are happy with the Belles sound - matching apples to apples at least in price and upgrade, Belles has the SA-101 and is about $2.5K cheaper then the INT-150A. and about $1K cheaper then the X150.5.
However as Tvad says the final determination would be your ears and what you like.
FWIW - I would invest in a Pre-amp, if it was me :o).
Only familiar with the Belles 150A and the XA 30.5 Pass gear, but between these the move is definetly not lateral. Do you have a Pass dealer near you? This might really require an audition for you to decide - the X series is certainly a bit different sounding thatn the XA.5s
Thanks for the responses! I think that my Dynaudios would benefit from more power than the 30 watt XA 30.5, even if the sound is more liquid and refined. If I get to hear the INT-150, I'll post my impressions.
I don't think you can wrong with most anything by Nelson Pass. Good luck if you go that route!
Anyone have experience with Belles Reference 350A and Pass X-150.5, NOT XA series? XA is more expensive than both of these similarly priced competitors and considerably lower power.