I had one baby that hated to be swaddled and one that loved it, so I'd maybe only get a couple and wait and see what they they like. Similarly, our Moses basket went unused as DD wouldn't let us put her in it, but DS had an along-side crib that worked much better.
YY to muslins, lots of. And wipes, extra soap, hand gel - you'll be changing a lot of nappies! Oh, and actually, we bought a spare cheap changing mat, and kept it under the sofa, along with a pack of wipes and some nappies so we didn't have to carry them upstairs every time they needed changing.
Sleepsuits and vests in various sizes. DD was born too big for newborn ones, and had to go straight into the next size up, whereas DS was drowned in them and DH had to go and get him some Tiny Baby ones (he wasn't even prem).
Some kind of sling I always think is helpful. I really rated wallet-style changing bags over the big, full bag style. They hold wipes, a few nappies, a changing mat, and a small tub of sudocrem (also get sudocrem!) and can be stuck into your normal bag or under the pushchair. If you formula feed I imagine they're less useful though as you need to take that with you too.
Oh - and for mum, a thermal mug with a lid. I used to spend so much time trapped under feeding or sleeping babies, never able to drink my badly-needed tea and coffee while it was hot! Now I buy every new mum I know one of these, so they can enjoy a hot cuppa without fear of spilling it on the baby!
Good luck. I'm jealous - no chance of more babies for me, and I miss them.