Your LM head probably has an Ohm limit of 4 Ohms. Do not go below that as you may damage your head. If you have the Hartke 2X10 XL it is an 8 Ohm cabinet, 1 or 2 of these will be fine, but don't use 2 and the 1X12. The Berg (I don't know if it is an AE or HT model) is also 8 Ohms so if you want a 2X10 + 1X12 config it will be fine, or if you want a 4X10 config it will be fine, but unless you get a head that is capable of going down to a 2 Ohm load you will not be able to use 3 8 Ohm cabs with this head. All the best to you in the future. Cheers.