Hey George, the MDRT is a very good idea as it's a much better transformer, and even more so as the 3TM has an additional tube so will draw more power (a feature of the MDRT is more and better power available (http://www.marshalljmpmodshop.net/miscellaneous_parts_and_replacement_tubes.htm)).
For power surges (which it's sounding like ?), you can use a power conditioner (Furman seems to get the nod around here) or use a computer uninterruptible power supply (UPS). I use a 1kva UPS with my MP2 rig as we typically run off a generator and the MP2 shits itself when the voltage drops, display goes hieroglyphics and I have to power cycle it to get going again (really great in the middle of a solo NOT
). The Furmans are quite expensive here in Oz >$500 AUD, The UPS cost me $160 but down side is the battery in the UPS will go eventually.
Cheers R