I have a Rpi 3+ and I am using the onboard WiFi and BT. My PI is in a plastic case. My Windows laptop gets around 275MBps on wifi whereas the Rpi 3+ get's about 70MBps. Is this what I can expect for Wifi speeds. The PI is in the same room as the router and I am connected through 5G. No walls in between. I have line of site to the router. Would disabling BT help as I have a BT dongle. In the past, the BT adapter had issues with the PI and kernel based on the lsusb number but that was awhile back.
That's about as good as it's going to get with the onboard WiFi
I would go so far to say that connecting your xbian Pi via wifi will lead to difficulties with it as an HTPC: you can't count on constant wifi speeds like you can a wired connection.
It's not too bad as long as there isn't a lot of distance or interference but wired is much better.
I'm a couple of meters away. I could get a repeater and a USB Gigaport adapter and try to get more speed. I saw someone did some tests and this gave them the most speeds but I'm not sure if it's worth it?. My router was having problems (slow speeds about two months ago fixed by a hard reset) and it finally stopped routing internet so I ended up installing OpenWRT and the router is working again. I may wait and see how it goes with the new router config. I have both bands going over the same SSID.
I installed OpenWRT and now the router is functioning once more.
Might be just my Pi3B+ but the onboard WiFi was very unstable and it was literally just 2 meters from the WiFi AP.