Pretty much everyone who has followed this thread from the beginning knows I am a fan of the LSR708i
We've done lots of listening tests here, between the 708s, M2s, Revel F208s, Revel Salon2s, Revel Concerta2s, etc.
My thoughts overall: Revels are silkier and smoother sounding, the JBLs have greater dynamics but can sound a bit "harsh" with music to some people. Both have an amazingly similar tonal balance. For orchestra and most music, I really really like my Revel Salon2s.
So much I could say but I'd write a novel, lol.
I used the 708is as LCRs for about a year and blew away many people during demos. Eventually I moved the 708is to surround positions and put M2s in the front for LCR. After our Salon2 vs. M2 shootout, I put the Salon2s up front with a Voice2 as center.
Now I will be installing SCL2s as LCRs behind the screen and will keep the Salon2s and Voice2 out in the room. Now I can demo the JBL sound AND the Revel sound
, for that size room, I think you would do just fine with the 708Ps. You might also consider the Revel F206 or Revel M106 at similar price points.