Last of the Marantz 1607s are being sold off at US$500 here, so probably GBP500 in the UK.
Newer Marantz 1608 is US$750 so probably GBP750 in the UK.
Both are 7.2, Atmos enabled, and 4K Ultra HD/60Hz full rate pass-through with HDR, BT.2020, 4:4:4 Pure Color support; full HCDP 2.2 support. and 4K Up-scaling, so about as "future proof" as anything these days.
You pay a bit of a premium for the "slimline" profile and power is down compared to full-height boxes, sinply because there's not enough room in the cases for the bigger transformers and / or power capacitors.
I am still looking for a 1607 for our house living room, but may opt for a full height 9 or 11 channel, merely to drive more "zones" than just the living room - our dining room, bedroom, bathroom and patio are all pre-wired for "muzak" speakers. It all depends on what the Memsahib will tolerare and / or if she'll let me cut a hole in the back of the sideboard that serves as our TV stand so I could put a bigger receiver inside, instead of on top of, said sideboard.