hmmmm, is your 'old' machine fairly new? Not vintage?
... I hesitate to even mention how many machines I have but I will say that DH has never told me that I had to get rid of something in order to get something else.
If the new machine is pretty expensive and the old machine still retained enough value and was already paid for, and as you said, you got a real good trade-in, then it makes sense to go ahead and trade it.
My embroidery machines are so old now that I doubt I could get any kind of decent trade-in value for them - so would probably keep them if I ever decide to upgrade....
Have fun learning your new machine.. oh ho - I just looked up what it is - no wonder - looks like you'll be having lots of fun..