i have a epos els303 floorstanders(front) wharfadale diamond 9cc(centre) wharfadale diamond 9.0(surround), q aucustics 1000si subwoofer,partnered witm my dsp ax763,i would like to know where should i upgrade amp or speakers,the sound is quite good but i could do a bit better as my room is quite big,so i have my sofa in the midle of the room and setup againts the wall.please any advice would be great.