How much magnification do I need to see the red spot on Jupiter?

It is more a question of aperture rather than magnification. I've found 6-inches to be about the minimum for seeing significant detail on the planets. The actual top magnification your scope is capable of is around 180x (based on tests I made with the same scope). 225x will be "empty magnification": you will just be magnifying the blur in the image. 180x should be enough power to see the Red Spot if you have excellent seeing conditions, but it will be a challenging observation. Train your eye by sketching Jupiter and be patient. The Red Spot is reported to be very clear this year, but more orange than red in colour. Often the colour is what you will see, rather than the oval.

Great Red Spot Transit Times

I tried to see Jupiter's Great Red Spot the other night. I could see the 2 equatorial cloud belts at 75x, 112x and 118x but not much detail. At 150x, Jupiter was bigger but had less detail. I looked for about an hour but didn't see the GRS. I think it was a combination of my first time looking for it, the seeing conditions and possibly the collimation of my scope. I hear the GRS is hard to find even in a 6 inch scope.

It's probably more than enough power. The Great Red Spot isn't always visible, and when it is it's not all that prominent. Seeing it will take some work.

how much does a telescope costs to see the space station