PSU form factor question

Some ATX power supplies are about an Inch longer, but will still fit in most cases.

Yes, almost any ATX PSU will fit in almost any ATX case.
All ATX PSUs have the same width and height. The width is 150mm, the height is 86mm. The depth varies between 140mm (some units are as short as 125mm) and over 200mm, but usually they are 160mm and 180mm.

ok cool thanks guys!

Any ATX PSU will fit in any ATX case. The only dimension that typically has some variance in ATX sized PSUs is the length; high capacity PSUs tend to be longer.