The other thing to consider is where your streaming needs are headed. Wireless is not ideal for streaming HD (let alone 4K) content, especially if there are other devices splitting up that wireless bandwidth. If you expect to have multiple devices streaming HD using that same wireless signal, your available bandwidth and quality may suffer, and you may want to consider running ethernet lines to certain areas.
For me, I have this setup:
Cable line to Modem to Router (4 ports)
Ethernet line from Router to Office SWITCH, split between Desktop, Tablo (OTA DVR), File Server
Ethernet line from Router to Living Rm SWITCH, split between Xbox, Roku, PS3, Receiver
Ethernet line from Router to Basement SWITCH, split between line up to my bedroom, and later some devices in basement (unfinished for now) and maybe other bedrooms.
Meanwhile any handheld devices (2 laptops, 2 tablets, 2 phone) are fine using wireless. That might change if we have kids and they start hogging streaming bandwidth too.
Obviously that may be a bit of overkill for your needs. Where it is similar is that I have a roku in my bedroom for streaming netflix or watching my PLEX server. Even with top flight routers (retail $200+), I still had buffering on my SD TV when streaming movies even though it was on the same floor and only separated by two walls and one decent sized family room (maybe 30' as the ghost flies?). Rather than buy a repeater, I ran an ethernet line down through the floor, across the basement ceiling and up to my bedroom and now the signal is perfect. The cost was $10-15 for the cable and my time to drill holes, run cable. Now it streams beautifully and more importantly is future proofed when I feel like putting an HDTV in my bedroom (for now I'm quite content to fall asleep with a 27" SDTV, which makes my older movies look better)
Regarding proximity, my guest bedroom roku that is only about 20' away from the router (with 2 doors and 2 walls inbetween) works great on wireless. This is used rarely for guests so I'm not going to run a line until necessary (ie 10+ years from now when a teenager needs a steady signal)
I'd move the WAP to the middle of the house first. After that, consider whether running a line to the basement would be feasible (and more affordable)