I feel your pain. Really, I do. There is simply no way not to miss Magnepan's magnificent ribbon tweeter once one has been spoiled by years of listening to music via the use of such a perfect transducer. I say this as an individual who disconnected his 3.7s last week because my room took on another purpose which shrank the space I can allocated to speaker placement - the 3.7s were 9'3" off the front wall. In their stead are my daughter's (long story, but she'll have my modified MMGs) Definitive Technology Mythos ST speakers, which certainly have strengths of their own.I'm kind of capped around $2000 or so, I'd guess. The basement room is very small. Everything would need to be reasonably small. I had a set of Reference 3A Dulcets I loved, which I now wish I still had. They had great imaging, no real crossover and a wonderful midrange.
I really wouldn't mind a 2.1 system. The main thing I'll miss is that giant true ribbon tweeter in the maggie 3.3R's. It goes down beneath 2khz, really helps when a single driver covers so much. I need stereo magic more than good surround sound.