Thanks Bremen. That's right, that's what I am trying to achieve.
So based on that, given that my second router is likely to cost more than the media bridge, perhaps I should just wait for it and sell the 2nd router now? (To avoid any confusion, I have two 87u - one in use downstairs and feeing powerline Ethernet, the other still boxed for use with the upstairs computer).
What I was essentially asking was whether using that 2nd router could be justified from a cost perspective if it gives me something the media bridge never will?