Unfortunately, the metal tool business doesnt run like Priceline-

"I am willing to pay up to $800 for that new $40,000 BMW"

That is to say, you dont get to pick your price, and expect the market
to follow.

I am unclear if you are just straightening angle and channel that
bolts on the side of equipment that rack mounts, or if you are
actually flattening pre bent angle into flat sheets?

But either way, it sounds like you didnt exactly buy the right tool
for the job.

I often have to straighten bent pieces of sheet metal- and I use my
big Chicago Finger Brake. Cost me 3 grand, used, which was deal as
they cost well past 6 grand new.
It will flatten and align channels as small as about 3/4" inside
measurement, and works great on angles- the big main clamping bar
weighs 500lbs or so, and is easy to clamp with one hand. Then, if
needed, I can bend the lower leaf up and get correction on angles or
channels.

If the metal you are working with is 20 gage steel, which is what I
would guess, then a $500 chinese brake might do the job.

A hydraulic press is best used in places where no manual feedback is
needed- not exactly the situation for fine tuning bent stuff.Unless
your bent stuff is 2" shaft.
Frankly, you might be better off with just a big, heavy vise, bolted
down to the floor, with some jaw extensions. Then you clamp your piece
in, and just yank on it by hand, or use a big crescent wrench to
straighten it out.

You can also do quite a bit of fine tuning on stuff like this with a
hammer, and an anvil, or even the edge of a 1/2" plate steel table.

On small, tricky stuff like this, patience is gonna get you a lot
farther than tonnage.