Ta.I did fit my Yamaha AVR in it but was a little tight with banana plugs. Tv height is not adjustable but I had a Wharfdale 10cc centre speaker under it and that fitted fine under my 48" Samsung.
Looking at the instruction manual, it doesn't appear that there would be any problems with leaving the back off as the internal shelf and the TV mount are otherwise supported. Would you agree?
And I'd second Nick's request for a quick measurement if possible. I'm sure my centre speaker (15cm H) would fit under my 42" TV, but I'm going to upgrade to a 55" HDR in a year or two, so I'd probably need about 52cm from the cabinet's top surface to the exact centre of the mounted TV to fit in the speaker.