Anything Goes : Is it possible to create quality Audio/Music masters on sub £1000 monitors? by Dan Backhouse

Hi, I'm getting more and more into mastering and I'm in the market for some new monitors for my own composing and mixing and if possible mastering of other people's material. I was Initially looking to spend around £500 however researching I've realised that for that price clearly they just aren't good enough so gradually the budget's been rising and I've recently come across the Mackie HR824 MkII's for £940. I'm interested to hear what you think the real limits are to stand a chance at mastering audio/music. I've read threads with people saying they wouldn't want to master on anything under £4000 which is simply far too much for me at the moment. Also whilst I think exceptional mastering could be created on 4k monitors I'm not sure I believe good masters cannot be produced cheaper monitors What do you think the limits realistically are? Also if you know the Mackie HR824 MKII's your opinions would be great :) Thanks, Dan