When you listen to the Artist 5s, do you feel a lack of sub-bass or bass?
Not particularly, no. But for most of my usage, sub bass is not an issue anyway (not in the mix). Bass (aside from sub-bass) is well represented in general.
My room acoustics won't be ideal probably, but I don't want to have to go out and buy a sub because of that.
Ours are not either. But a few sound absorbing panels go a long way.
How "nearfield" are these? What's distance do you listen at and what's the ideal distance would you say?
Not sure I can say. For my use of them, they are at my mixing station in studio. I have them roughly 1m away, and 1.5 m apart, with a 30 degree toe in.
Lastly, what are your preferences? Or, better yet, what headphones do you like & what don't you like?
Sound wise. I tend to gravitate towards mid and high centric cans, with lots of detail. I do my headphone mastering with a set of EQ'd AKG K702. For pleasure listening, I use the 702, Grado 225, Sennheiser 600. I did not like the Senn 650 as much, but I did enjoy the 595 and 555. I have never found an ultrasone I could stand. And as much as I wanted to like them, I didn't enjoy the Denon 2000 or 5000. I've not tried any of the AT's.
We also use K240 and 271 AKGs in studio, but outside of that purpose, I've never really compared them for pleasure listening.