Here are the names to watch with an estimate of their likelihood at #56. Unscientific guessing, obviously. (Green denotes a player that I think would be a draft steal at #56). An asterisk (*) denotes a player that did not play DT in college, but has the potential for a move.
Datone Jones (0% to 10%)
The fastest and most productive DT in 2012, but has short arms and inconsistent tape. Finished season on a hot streak. I'm a fan. Opinions are mixed- could slide some- but probably won't.
Kawann Short (10 to 20%)
A great finesse DT that knows how to slip through gaps but isn't much of a physical force. Consistent year to year. Productive. Great pick if he's there at #56.
Sylvester Williams (40%)
Williams could slide because I don't think teams view him as a player with tons of untapped upside. He's more of an Allen Branch type than a Jason Jones type. Good player, and given the lack of alternatives, I'd be fine with taking him in the 2nd.
Brandon Williams (70%)
Huge (341 pounds), slow, but surprisingly he's a better pass rusher than run defender. One of the strangest 3-tech's you'll see. I think he's our most likely pick at #56.
Bennie Logan (80%)
Big and has decent athleticism, he's a well rounded DT that I think will be a league average DT. A poor man's Sylvester Williams.
John Simon (80%)
A favorite of mine. Some people have Simon going in the 2nd, others in the 5th.
*Malliciah Goodman (80%)
Extremely similar to Greg Scruggs in terms of speed, size, weight, arm length, and lack of experience at DT. Scruggs is better though and he was a 7th round pick last year.
*Lavar Edwards (80%)
Edwards is probably the closest thing to a Jason Jones in this draft (very similar height, length, arm length, speed, athleticism). Only problem is, he never played DT, so we don't have the best idea of how he'd handle that move.
*Joe Kruger (80%)
Like Edwards Kruger also didn't play DT, but as a DE he showed good strength and posted Jason Jones type measurables at the combine.
Nick Williams (~100%)
There is nothing of Nick Williams on youtube, but he comes from a small school and posted good measurables. Could be a surprise candidate or he could just be something to watch in the late rounds.
There are other DTs worth noting (Jordan Hill, etc), but I think the rest of the list will either safely reach our 3rd round pick or they aren't 3-techs.
P.S. Hughes is not a 3-tech, IMO. Zero pass rush ability, undeveloped and struggles with interior run defense, but he has a ton of anchor and pure core strength. Very similar to Red Bryant.