I put castors on mine. The cab had little wheels that you could use if you tipped the cab back a bit, but essentially useless for positioning purposes.
I put 4 heavy duty castors on mine, and regularily move it - it's on a carpeted floor that I need to move to vacuum. I'm also tall, so the extra bit of height it adds is nice for me

I ended up carrying my cab from my basement to the main floor by myself - lifted the thing right off the floor with nothing to support it. I wasn't aware I was doing this until my moving partner informed me. I'm glad I didn't give myself a hernia. Once it was on the main floor, I put the TV and guts in - stuff too fragile to be banging around while going upstairs

.
In short, the castors made the whole thing WAY easier to position. It's a VERY good idea to put them on.
Odonadon