Personally, I like the look of a full pot with lots of pups around the main plant. I would re-pot the one with the most pups.
I'd use a slightly larger pot with LOTS of drainage holes. Use a cactus mix and add extra grit to make it very fast draining.
I would keep the best one and re-home the others. Then you'll have some room to get some more Echinopsis with different color flowers. The flowers are spectacular, and are available in a variety of colors.
A word of caution:
These are usually columnar in form. Can you see how the newer growth is starting to look like a hot air balloon? I'd toughen them up, a lot, before they get totally out of shape. Way less water, more light, more heat and no fertilizer. They should go dormant in winter.
During the cooler, darker winter days they need a rest. Water lightly only once a month. If you can, add a grow light over the top.
They do best in 80F+ (27C) heat and bright light.
Cacti are difficult to keep indoors, especially in northern locations. I think you're doing quite well, just be careful about over watering. These plants don't just tolerate hot dry bright desert conditions--they require them.
Here's mine, it has a bit more pink. There are lots of spectacular colors available...
Wow, thank you Lucy, that one with 50 pups was a pup 2 years ago! I'm going to have to find homes for the 70 pups I have as I'm outa space, below is the flower! Amazing 
