Ok, so most registers actually output current while mine "sink"s the current (inputs the current per-say). Is this correct?
I am using this all to control an LED array. I am using the registers to control 25 columns and 15 rows. The plan is to sink 1 row at a time and make the columns provide the power so that each LED has it's own power supply, giving maximum brightness. I am using the transistors to switch on-off the power to the columns, thus giving total control.
Maybe it makes more sense to get simpler output-current registers for the columns while using the sink-current registers for the rows? This would make the transistors easier to use (if I would even still need them, depends on how many LEDs I am trying to power I suppose). Is this a correct thought process?
Yep, that is correct. Use something like a 74HC595 to power the LEDs, and use your existing shift register to sink the groupings (columns, rows, whatever).
If you are going to have lots of LEDs connected from one output of the 595 and have them illuminated *at the same time* then you will need a transistor, but as it's a "high side" switch, make it a PNP, not an NPN.