After building a bunch of stuff from IKEA over the years, I personally wouldn't trust something built out of the box to take the weight unless it was a bed frame... Then again it depends on the bed frame...
I'm REALLY not a fan of mixing particle board with an aquarium. Even if the stand were rated to hold that much weight to begin with, just one slightly messy water change is a major risk to anything made of particle board like most Ikea furniture is.
I'd keep checking Craigslist for a solid wood stand.
Does Big Als still carry their Stingray stands (been a long time since I looked)? Those were pretty economical and had nice clean lines.
Attach a sheet of 1/4" plywood to the back, with lots of brads, to reinforce the unit against side loads, and it should work fine for a 20-25 gallon tank, as long as the tank is 30 inches long, not shorter or longer. Just don't allow a steady leakage of water to soak into the particle board. But, who would do that?
The 44 pound load limit is with the unit mounted on the wall as a shelf unit, not sitting on the floor. It would take a lot more than 44 pounds on the vertical boards to make them collapse. If you see one in the store try sitting on it.
The issue with the 44 pound limit is not just a vertical weight limit it is also horizontal. If there is a shift of weight horizontally, say someone bumps into the side of it, the wooden dowel pins holding the top of the unit as well as the base will snap and most likely pry out the metal pins that lock with their proprietary nut. Without significant bracing I'd keep away from it. If this was made from solid wood or joined lumber I would have no concerns, particle board though is always a risk when it comes to weight and water.
I'll have to see what my aunt and I could do. Don't have it or the tank yet. Working on saving up but are there any nice rimless/frameless tanks that would fit nicely on it. Still doing my researching & Googling. And before the tank my room needs some work done to it before I can start on the tank.
I'd generally be hesitant to put a tank on most of the IKEA stuff.
If you get a tank that matches the length of the stand, so that the side portions of the rim are directly over the uprights of the stand on either end, I think it would probably support the weight. If the tank isn't long enough, so that it sits between the uprights, that top piece will sag, and that will put weird stresses on your tank, and possibly lead to a leak or failure.
And Hoppy's suggestion of putting plywood on the back will make the stand much stronger in terms of racking/twisting (like the scenario Archerofthemoon mentioned).
It might be worth checking for old/used furniture, if there are any salvage type stores in your area. Stuff built several decades ago was usually built pretty strong compared to most of what you see around more recently.