You can hook up as much as you want to the LV transformer, but it will act as a choke. It can only accept and output so much power per tick. If you want more EU throughput, you should add a second LV transformer.
And we know what cables to use because we read the Industrialcraft wiki
Just attach the MFE to another LV transformer so that it feeds more EU into the system.
Tin is extreme low voltage at 5 EU/packet with no loss over 40 blocks.
Copper is LV (32 EU/t) with 1 EU loss after 5 blocks if insulated.
Gold can take MV (128 EU/t) with about 1EU loss per 2 blocks depending on insulation
Glass fibre is HV (512 EU/t) and only loses 1 EU every 40 blocks.
High voltage cable is extreme voltage (2048 EU/t) with about 1 EU loss per block.
Transformer upgrades aren't that expensive. You can use them to allow most of the IC machines to work without needing to worry about the transformers. Most of the machines operate on LV (32 EU/t), if you add 1 transformer upgrade the machine will work on LV or MV (128 EU/t) and if you add a 2nd transformer upgrade it'll work on LV, MV or HV (512 EU/t). Just be sure to install the transformers BEFORE connecting them to the power grid. Also be sure not to remove the transformer upgrades from the machines while they are connected to a MV/HV power grid.
If you want to do this you can set the output of the MFE's pointing towards another MFE and so on until you get to the final MFE which needs to have its output facing the cable connected to the transformer or just to the transformer itself
For the cables its like this
Tin = 5 EU/t Extreme (very low voltage)
Copper = 32 EU/t (low voltage) It loses 1 EU for ever 5 blocks if insulated and is good for starting of with
Gold = 128 EU/t (medium voltage) It loses about 1 EU over 2 blocks and is probably not the best wire to be using unless you have no diamonds for glass fibre
Glass Fibre = 512 EU/t (high voltage) It loses 1 EU over 40 blocks and I would advise using it as long as you can afford it because it loses very little power and can handle high voltage
High Voltage = 2048 EU/t (extreme voltage) It loses about 1 EU over 1 block and you would probably want to use it for a nuclear reactor and maybe some other items with extreme outputs