Satie over at the Planar Speaker Asylum has a pair Tympani T-IV’s which he bi-amps, using a Crown 2000wpc amp on the T-IV bass panels! Magnepans recommended T-IV bi-amp x/o is non-symmetrical, low-pass 18dB/octave at 250Hz and high pass 6dB/octave at 500Hz. The recommended bi-amp x/o for the T-1A is symmetrical, 6dB/octave at 1000Hz for both high pass and low. Playing up that high, the amp for even the bass panels needs to possess higher sound quality than if used to only 250Hz.
The Sanders Magtech amp would be great, if your budget allows. Bi-amping allows the use of two smaller amps, a tube one for the m/t panels being a potentially great sounding possibility. I will soon be setting up my T-IV’s, using a 400wpc (@ 4 ohms) solid state amp on the two bass panels and a 100wpc tube amp for the m/t.