Will this hold my 63 pound black beauty??!!

You could also consider your local glazier for custom thicker glass. 

I wouldn't take the chance. I'd put the amp on an amp stand and keep it on the floor.

there are two load characteristics which may be of interest

load point capacity  - how much weight a floor will hold per unit area.  The common example is the displacement of a woman in high heels.
At some measure the weight at  the point of the heals and soles will crush thru.  generaly in pounds per sq. inch

floor load capacity - how much total weight that glass and it's support  mechanism hold before crashing down

you might test the later by stacking workout weights or 10 gallons of water

IKEA LACK END TABLES.  WILL COST YOU 10 BUCKS. THEY ARE MADE OF BALSA WOOD. RICHARD VANDERSTEEN LOVES BALSA FOR HIS MODEL 7 MIDRANGE DRIVER.