From left to right:
Infinity IRS Sigma, Boston Acoustics Lynnfield 500L II, SSR, Seas+OWI mini.
The Infinities sound the more colored of the 4, but they are a pleasure to listen to, with lush and warm highs(not that extended) and mids, very clean but not that powerful bass, despite the 12" woofer.
BA and SSR sound very similar above 60hz, very flat and accurate, clean mids and extended highs, with the SSRs getting a node in soundstage and treble extension. The Boston bass Q is amazing.
The Seas-OWI is also flat and accurate, with a smaller sound stage but great imaging, but sounds a bit sterile and lifeless (colorless?) compared to the others, which is not a bad thing for monitor use.
Now all of these speakers use excellent drivers, and the way they sound is mostly a result of cabinet design and crossover decisions.
The SSR cab has standard ported version dimensions provided by Rick.
I would say, if i had to choose 2 pairs, it would be the Sigma, and the SSR with a great sub.