Cathe does power stepping, so she adds propulsion to a lot of moves even on the step, but she also always reminds you to modify any move to suit you. So you would still get a tremendous benefit out of her stepping even if you leave the jumping out. But you might find that jumping on the step absorbs a lot of the noise and shock to your bedroom floor, so you might be able to do it. The only things that involve high impact aerobics on the floor itself are tapes like MIC and some of the Crosstrain Express workouts have sections of hi/lo. But again, pretty much all of her moves can be easily and obviously altered to be non-impact and they'll still be tough enough to get you sweating and working.
What kind of cardio do you like to do? It's hard to just recommend one out of the blue without knowing more about you. Are you looking for something super challenging? Personally, I love Bodymax, Interval Max and Circuit Max. If you want some moves that are powerful but easier to follow, I find Powermax to be tons of fun, really tough, but a slightly slower tempo so it's a good Cathe tape to start with, and the moves you learn in PM are in a lot of other tapes so it's a good place to start.
I'm also in week 4 of her Crosstrain Express 6 day rotation and it's been fantastic. Never boring, every workout is great and really diverse, and my body has been responding so quickly. You have to buy them as a set, so that might be more in the future for you, but it covers everything; step, hi/lo, kickbox, intervals and weight training. Great ab work too.