If you used 360 multibuilder correctly and created an image with dash hack patches, then you should be fine there. Some ppl have reported better luck with v0.2 as opposed to 0.3 so you could try that.
But First! You will boot into Xell if you power on with the EJECT button. That is by design so if you're still out of the case and it's mobo and rf board attached power on with controller and see what you get.
Hope you get it sorted man keep us posted!
Edit: This is assuming you are doing RGH and don't have a jasper with too high CB