Well, GENERALLY speaking, strength increases amount to size increases. If you eat enough food/protein, and don't do singles all the time, then you'll gain size. That's just how it is.
HST is also a worthwhile program. Both DC and HST are light-years ahead of 5x5 and volume training for mass, IMO. Actually, I still place 5x5 under the volume-training category, so that's somewhat redundant.
Here is how I would compare DC and HST.
-Both are good for mass gains. HST should theoretically be better, but in my experience and others that I know, DC has resulted in faster gains.
-DC is geared towards gaining strength quickly. HST not so much (though you will gain strength as well)
-DC is a bit simpler to follow.
So really, if you can put forth the effort, your strength and size will shoot up on DC faster than you'd probably believe.