I've had extensive experience with 3.5R's and you need serious tube power to make them work as well as with a high quality solid state amp. Unfortunately, high power tube amps don't come cheap. We're talking a mandate of 150+ watts.
The autoformers will help (expecially with OTL's) and cure a few problems. Fortunately, Maggies are a mostly resistive load, so they don't change sonically as much as other combinations. IMHO, this applies to speaker cables as well, I wouldn't throw a lot of money at speaker cables expecting great change, just subtle changes, so watch your wallet and audition as necessary.
To be honest, I'd consider sticking with the Plinius line with a dedicated amp and using a tube preamp to help get the sonics timbrally more correct. I was told a long time ago by a dealer that if you have Maggies, you need tubes somewhere in the system. I would have to agree based on my own experience. Another great match seemed to be big Pass amps. Bryston mono's are maybe less sexy, but seem to be a very good match as well with most maggies, especially the larger panels.
With all that said, large VTL's tube amps will sound a little sterile, but have great control. Big OTL's will ruthlessly reveal upstream problems, but strike a nice balance and sound very natural. Big ARC tube amps like VT-200's set up as monos will be all right, but may grenade with a tube arc-over so they're a bit stressful during loud passages. LOTS of tubes per amp will sound nice and look great at night, but you will need all those tubes to make the 3.5's sound better than a good SS amp.
Also, watch your midrange fuses during loud passages, when the fuse pops, it seems to shovel more power to the ribbon tweeter which is more fragile.
Good luck,
RFG
