it would seem to me that most any brand can do the things you want to do, and the printer you'd likely have to buy separately anyway. Dell does in fact offer computers with a terabyte of memory, though if you ask me you'd have to have some particularly hard-disk-devouring hobbies to actually need that much. The poor performance of your current computer can be caused by lots of things, but I rather doubt its being a Dell is the main factor there.

I'm not trying to convince you not to switch from Dell - I've no idea what the best computers at the moment are, quite possibly they aren't Dell's - but I found your arguments against them not too convincing.