I'm kinda new to the plannar/magnepan world, but I am really interested in trying out a pair after all the reviews I've been reading. From what I understand these speakers are quite power hungry. What is the minimum I need to properly drive these? 
I currently have a VAC Avatar integrated tube amp. These are the stats:
Type: Integrated vacuum tube amplifier with MM phono stage and home theater (direct power amplifier) mode.
Tube Complement: two 12AX7 low noise (phono), two 12AX7 (line stage), three 12AU7/6189A (power amplifier), and four EL34 (power amplifier)
Options: Remote control for volume (motorized direct control) & mute
Power amplifier ("Home Theater" direct mode):
Output matching: 4 or 8 ohms nominal
Power output: 60 watts/channel ultra-linear; 27 watts/channel triode
Frequency response: 9 Hz - 35 kHz +0 / -0.5 dB, 3 Hz - 71 kHz +0 / -3.0 dB
Power bandwidth: 11 Hz - 63 kHz + 0 / -3.0 db ref. 50 watts
Gain: 25 dB ultra-linear; 23 dB triode
Residual noise: 1.5 mv at 8 ohm output
Channel separation: -72 dB @ 1 kHz; -60 dB @ 10 kHz
Line stage preamplifier:
Gain: 24 dB
Maximum input signal: Infinite (attenuation precedes line stage)
Noise contribution: Approx. 0.1 mv at power amplifier output 
THD contribution: Approx. 0.04% 
Tape output: Unity gain from selector, non-inverting 
Phono stage preamplifier: 
Gain: 37 dB (measured at tape output)
MC phono stage in place of the MM optional 
Residual noise: 3 mv at output (S/N ratio approx. 69 dB) 
Overload: 117 mv @ 1 kHz = 8 volts RMS output, 460 mv @ 10 kHz 
Frequency response: RIAA +/- 0.25 dB 
Notes: Does not invert absolute phase. 

Anyone know if these will do or if I'll have to upgrade? Love the tube sound . . . will I need to go solid state for Maggies? Thanks for putting up with the noobie question :) 
while the the 3.7 is a physically larger speaker than a 1.7, Maggie themselves will tell you it is acoustically smaller

so will sound better in a smaller room

3x more spendy tho

When I say low level detail, I'm referring to minute details such as decay of a piano, or revealing of things you hear in older jazz recordings in a quiet passage such as a chair creaking, or the subtle brush of a those areas I thought the Bryston was better.  The X350 is certainly no slouch in the bass department......

The overall signature of sound for 7s versus 28s is so very similar, that if a person's wattage/headroom/room size needs were served by a pair of 7s, I would stick with it......I had a chance to get a pair of 28s for not a huge amount for upgrade, so I went for it......and while it's true it sounds like there is more headroom, the 7s still sounded similar for half the money.....but the 28s aren't leaving :)
I think my listening room is a bit on the large size, so guessing the 1.7's would be better suited? 
Setup is in my living room area which merges right into the dining room, so it's a good percentage of the whole house. The whole house is about 2100sqft, so I'm guessing living/dining area are about 700-850 sqft, roughly

Thanks stewart, was it the X350 or 350.5 you owned?

Based on what I´ve heard the .8-series should be more neutral vs the more lush sounding .5´s.

I think my listening room is a bit on the large size, so guessing the 1.7's would be better suited?

The 3.7 or 20.7 will work better in a large room. 

An oversimplification would be:
Small room - small speaker (.7 or 1.7)
medium sized room - medium sized speakers (1.7 or 3.7)
large room - large speakers (3.7 or 20.7)