We have been speaking about it ad nauseam for months now.
I think we can all agree we need one and probably a couple. However they are not all that common.
Leroy would be worth looking into, but the smoky that could come quite cheaply is Ita Vaea, provided that he is over his health concerns.
Given the favours the Brumbies have done Vaea I think he'd have a heart of stone to go elsewhere.
Houston wouldn't be the worst signing, hell at 27 he'd be a good one, but lets remember the Reds weren't great last time he was
starting so I wouldn't be touting him as a necessary signing for success.
If I was the Reds, and I was looking for a big number 8 who could start Super rugby, I'd look to the more established PI or Argentinian 8s. Think Tuifua, Levave, Tekori (though equally talented as an impact lock), Talei (also a great leader), or even Leguizamon (if you've got the cash together).
If you're willing to get ballsy, every Aussie Super rugby team is allowed a 36th contracted player who's Japanese. They don't cost much (because it's basically their off season) and they actually have a few big 8s with their starting one being one of their best (though a bit penalty happy). Their starting 8 Ryu Holani is great player and their 2nd 8 Kikutani also used to be good (and their captain) but just isn't quite there anymore.
Just some thoughts. Houston, to me, needs to actively want to come home to be a good signing because he'd need to be on potential starting player money, rather than established starter money, to be worth it.