The M3 uses different bulbs than the M2. The KT2 and KT1 is the same head, the bulbs are different. The KT1 comes with the N1, a 2 cell bulb for use with the M2,6P,C2 etc.
The KT2 comes with the N2 which is for the 3 cell lights such as the 9P, C3, D3 or 2 cell with A19.
You can have one KTx turbohead and use the N1 or N2, switching between 2 cell and 3 cell.
The M3 bulbs are larger, providing more light. The Turbohead for the M3/M4/M6 has Shock Isolation to protect the bulb. The KTx does not. If you want long range, the KT2 with a 3 cell setup will work. Your M2 will be 2 color if you use the A19 (comes in black only).
I don't explain things very well so if your still confused, the SF expert (Al) will be able to clarify your needs.