I don't think our need for an '8' is nearly as big as our need for a winger and a striker in this window. Since we've change to a 4 back we've been the 3rd best team in the league. The '8' were all after is the role that Cal and Kasey are playing. The fullbacks are still as attacking as they were in our 5 back system, meaning that we need a more defensively solid in the midfield (why Sheaf and Eccles are 4th and 6th in average rating for CMs this year). The most '8' midfield we have at the minute is Allen and he's looked a shadow of last season when playing in the new formation.
With the rumour swirling that Hadjis injury will have him out for a month our replacement is either Kasey or DaSilva on the left, afraid that isn't good enough for promotion. I don't think the right is as much of an issue as Cal or Milan can fill in on that side.
As for a striker, I think the sooner we replace Matty the better. He's been poor for the last 3 months and isn't a patch on Simms in the new system. He doesn't occupy defenders nearly as well as Simms does. Saying that I'm not sure Simmo is the answer up top in this system and Langstaff does offer something different to the both of them so could be the answer.