I've got two of those kits.
One bass drum has the stock heads, and the other has an Evans Emad batter on it. They both sound equally good to me - just different.
They do have a bit of a tuning range, but you aren't going to get a real
deep sound out of an 18" bass drum.
As far as an 'open' sound with a bit of resonance, the stock heads can provide that.
Really though, I'd say before you buy any heads for it, get a riser first. Lift up the batter side a bit with the riser, so your beater is hitting more in the middle of the head, and drop the front legs to level it out and get the whole thing off the ground a bit.
I've got risers on both of those 18" bass drums.
One has this: http://www.musiciansfriend.com/drums...p?src=3WWRWXGP
The other has this: http://www.musiciansfriend.com/drums...-drum-platform
Get that set up first, then play with the tuning, and if you're still not happy with it, then
get some different heads.
If you're still
not happy with it after that, they're probably not the right drums for you - LOL.