Hi Isophere, I must admit that I didn't think - overall - that sources, or at least digital ones in recent years, were vastly different. I wouldn't necessarily buy a supermarket DVD player as my main source, but but by the same token, I wouldn't lash the cash on the AVI player I use as a brand new item (£1500 in its day a decade ago). Until recently I had the Marantz SA7001-KI I mentioned, which was £600 on release. There's no way the AVI was £900 better. Not a hope, both are excellent players.
In my room, I have the stereo setup across the width rather than firing down the room and the speakers are just over 6-feet away from me and about the same apart, maybe a little more. So this isn't a massive space to play with. The Tannoys just own the space they're in. Anything bigger doesn't work as well (Pioneer S-71B - great speaker if you have room to spare).
So yes, speakers and amps first and then source - for digital. Source first for vinyl though. I've used a stack of amps for hobbyist stuf in the last five years or so. Now I don't follow a traditional hifi approach and use an AV amp instead (the Onkyo) and haven't looked back. The 818 has plenty of grunt, takes all of my digital source, music or TV and sounds excellent, the most important thing!
One other tip - spend time getting speaker positioning right if you can. It'll take about five minutes listening to a track or two to see where the speakers should best sit but it can potentially save you hundreds - people will spend hundreds on cables for a very minimal change but wouldn't think about moving their speakers around first.
So good luck with the search. Enjoy it though, it's fun. In the end, buy right, buy once.