XLS200 setup help

[Tman666]

I've finally received my new sub to replace my dead MS 409w, 1st impressions omg its tiny what have I done!!! (but this did please the wife) its about 1/2 to 2/3 the size of the old sub.
But then I switched the unit on and what a punch from a small box I can say I'm pleased so far. Im going to start setting the sub up properly this week ie not just plonked in the nearest spot.

So onto my point I have the crossover on the amp set to 100 HZ does this sound about right, I have the crossover on the sub set to full.
I also have the phase set at 0 as I'm not really sure what this does yet and the last sub only had a 0 or 180 setting?
Just waiting for the wife to go out b4 I start playing with the SPL, I gather I'm aiming a flat level over the range of sounds.
Im I right in thinking on the sub the only way to change the room response is by moving the sub about?
Any input would be gratefully received by a Av noob ie me

specs for the genie speakers im trying to match sub with are below
Sensitivity 86dB
Frequency response 95Hz – 20kHz

[Badger0-0]

Your thinking is pretty much spot on
Move it around as much as you can and try things.
Small tweaks with phase can make big differences.
And I'd go with a higher crossover on the amp, but it will be trial and error.