[Arm-netbook] Oscilloscope or bust?

[David Niklas]

Hi,
I need help here. I was designing the power supply of my laptop and I
noticed that some power bucks and step up/down converters (Which both
seem to do the same thing. Please tell me otherwise.), produced a more
stable power supply than others. In order to find out if they are truly
suitable for suppling power to sensitive electronics I've heard that I
need an oscilloscope.
I currently own:

1. #222634543946
"DC-DC 10/12/15/20A 150/250/300/400/1200W Step up Step
down Buck Boost Converter"

2. #152710861245
"2A DC Boost Step-up Adjustable Converter Module 3v-24v to 3.3v 5v 6v
9v 12v 24v"

After learning that some guy with an oscilloscope reviewed these, I'm
planning to get: #122923215542
"6 Pack MP1584EN ultra Small DC-DC 3A power Step-Down
Adjustable Module Buck M2H3 6 Pack MP1584EN ultra Small DC-DC 3A power
Step-Down Adjustable Module Buck"

I've seen many oscilloscopes online on crowd funding campaigns. I've
never been certain of which to get, if any. The real professional ones
are out of my budget range of about $100. *I'll pay more if I must*, but I
already did not anticipate the need to actually evaluate what should be
solid products.
I probably should find a solid adjustable DC power supply to test these
with vs. an old laptop power pack or some batteries.
What I need some of these things to do is to take a dynamically variable
voltage as input (Li-Ion batteries in series), and produce a constant
voltage as output. Others I need to just convert to the correct voltage
from the old laptop power pack.

Thanks!
David