Surrounds for Martin Logan Preface speakers

[Silo5]

I had a chance to listen to ML Preface speakers this weekend. I actually set out to listen to some Klipsch Reference Series speakers, but learned the shops in my area are either going out of business or don't carry Klipsch speakers anymore. Anyway, after listening to the Preface speakers, I was really impressed with them and will probably put them at the top of my list now. The set up I listened to had the Vignette as surrounds and the Fresco i as the center. Iron man demoed through this set up was utterly amazing. This set up is a little more than I was looking to spend right now, but well worth the sound. I was looking to see if there were other surround speakers that would work with the ML Preface that would sound just as good. ML Preface's are 4 ohms, so I'm looking for surrounds that are "ohm compatible". If nothing else, I would eventually get the other recommended speakers for this set up. I was just curious if there were other surrounds that would be just as good and not as expensive as the Vignettes. Anyone familiar with or own the ML Preface have any ideas/recommendations?