Problem with Arcam or JM LABS

I have an Arcam AVR 250 with an Arcam DV78. The speakers are JM Lab 716S Chorus Line(mains) w/ a JM Lab 700S Chorus Line (center) and JM Lab 716S (rears). The front 3 spkrs have Rega cables. The problem is understanding the dialogue from the center channel when watching movies. We think we have everything hooked up correctly and every setting set proberly. We have adjusted and readjusted every setting many times with little or no improvement. I have been running the mains on 0-5 with the center at 6 and the rears around 2-4. I purchased a sound level meter and set the levels correctly. No help. The voices coming from the center sound thick at times and slurred. We have tried the center at 5' and 2' with no improvement. The odd part is that I can understand every word coming from my TV during a broadcast when it is coming out of the center. Is there anything I can do to brighten the sound or is it just the British sound that I will have to learn to deal with. Thank you for your time.