If you do decide to get a separate HP amp, do some research first. The NS1000's are fussy about which amp they work well with. Some decent amps don't do a very good job with them.
I don't know which ones, as I've not looked into it enough. Uriel will probably know which ones are worth looking at.
Essence amp works very well with the NS1000's, apparently.
Not sure if the Titanium HD has enough clout. Creative claim that it can drive up to 330ohm headphones. A lot of people can't find a dedicated HP amp on the card though, so it's doubtful it will drive the NS1000's as well as the Essence.