DIY Surround speaker : Choosing LF and HF components to match the front speakers ?

Hi,

Many months ago, i have upgraded my 5.1 installation with 3 DIY speakers, instead of 3 Focal Utopia Micro Be.
These DIY speakers use an Altec 909, with a 811B horn, and a AES TD15M. A bss 366 is doing the active filtering and the EQ.

Now, the time is coming to think of the surround speakers upgrade (actually a pair of Focal 907Be).
It needs to go down to 80Hz (-3db) in a little enclosure. The distance between my central seat and the surround speaker is around 2m so i don't think a horn to be a good idea (?).

A non flat frequency response is not a problem because i will EQ it with a BSS 366. But i will use passive filtering.

I have absolutely no idea on which components could be associated to my front speakers to form a homogeneous 5.1 system.

So, if you have any suggestion :)

Serge.