Thinking of selling my pioneer SC-LX57 amp and getting one of the new Onkyo DTS X compatible amps looking at the tx- NR646 at about £550. I am leaning towards DTS X as opposed to Dolby Atmos is because I already have 9 B&W M1 speakers set up as a 9.2 configuration, and I don't want to really start having to add more speakers to accommodate Atmos. I realise the Onkyo amp is a lot cheaper than mine was when I first purchased it about 18 months ago but time and technology move on. I now own a Sony 65" 4K TV and would be interested in buying a 4k BD Player later this year. I really don't know what kind of price I could expect to get for my pioneer or even if changing these amps would be a good idea but I would appreciate any advice any body on these forums could offer. Thanks.