I have had my system for a number of years and when I bought it, it was highly regarded. However, it is OLD Pro Logic (remember that?), a Yamaha DSPA2070 which was £1200 back then. Honest answers please to; 1. Will I notice a marked difference in changing to Stereo rear channels 2. Would the advances in technology and drop in prices mean that a Yamaha 750SE amp would provide a reasonable change or would I notice a drop in 'quality' and need to buy a more expensive amp to maintain /improve the listening experience with movies. On the speaker front, I have what must look like an odd mix by todays 'matched set' options, but I am not sure that there is anything hugely wrong with what I have. The front pair are Proac Supertower II floorstanders The Centre is a Kef 100C The rears are JBL Monitor 1's (which were fine for Pro-Logic's limited frequency at the rear) The sub is a Rel Strata Mk1 Thats over £2000 worth of speakers historically and I'm not sure what I should do to ensure that I dont undo the benefit of upgrading the amp - presumably upgrade the rears at least. The room is 16 x 12, the leads are all decent (IXOS Gold scarts, Van der Hul phonos) and this is all linked to a Panasonic 36" TV, so any advice would be much appreciated.