Is 60squares 60 square meters?
I am not familiar with the 255's. I think they are also called the SM 255. Do they look like this?
Among the info I found on it was one site where a couple of people said they weren't very good and another where several people said they were great, but only if you had a large room for them.
Surprisingly, I think the sole review on Amazon is the best overall summary!
This from a Robert C. Babcock:
My take away is if you like rock/electric music, you should try these just to see how they strike you. Unlike your smaller HK's the SM 255 should casually fill your large room (assuming they are in good working condition) and is efficient enough that either the HK or the Denon can drive them louder than you would want to listen.
They sound like they'd be pretty decent at HT.
My only concern with the HK system is they are small speakers in a large room. The SM 255 most certainly resolves that. You might try them out to give you an idea of their potential.
However, if I understand what you are saying, you are happy using the Infinities in another, larger room. So I would look at the temporary test as a way to experience a speaker with more SPL capability and no concern of over-driving them.